{"segment":[{"time":24,"part":[{"title":"Kh\u1eb3ng \u0111\u1ecbnh \u0111\u00fang hay sai","title_trans":"","temp":"true_false","correct":[["f","t","f","t"]],"list":[{"point":5,"image":"","col_name":["","\u0110\u00fang","Sai"],"arr_ques":["Di\u1ec7n t\u00edch xung quanh c\u1ee7a m\u1ed9t h\u00ecnh n\u00f3n b\u1eb1ng chu vi \u0111\u00e1y nh\u00e2n v\u1edbi \u0111\u01b0\u1eddng sinh.","Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh n\u00f3n b\u1eb1ng n\u1eeda chu vi \u0111\u00e1y nh\u00e2n v\u1edbi \u0111\u01b0\u1eddng sinh","Th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh n\u00f3n b\u1eb1ng n\u1eeda di\u1ec7n t\u00edch \u0111\u00e1y nh\u00e2n v\u1edbi chi\u1ec1u cao","Th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh n\u00f3n b\u1eb1ng $\\dfrac{1}{3}$ di\u1ec7n t\u00edch \u0111\u00e1y nh\u00e2n v\u1edbi chi\u1ec1u cao."],"hint":"","explain":["Sai v\u00ec di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh n\u00f3n b\u1eb1ng n\u1eeda chu vi \u0111\u00e1y nh\u00e2n v\u1edbi \u0111\u01b0\u1eddng sinh","<br\/>\u0110\u00fang","<br\/>Sai v\u00ec th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh n\u00f3n b\u1eb1ng $\\dfrac{1}{3}$ di\u1ec7n t\u00edch \u0111\u00e1y nh\u00e2n v\u1edbi chi\u1ec1u cao.","<br\/>\u0110\u00fang"]}]}],"id_ques":1691},{"time":24,"part":[{"title":"Kh\u1eb3ng \u0111\u1ecbnh \u0111\u00fang hay sai","title_trans":"","temp":"true_false","correct":[["t","f","t"]],"list":[{"point":5,"image":"","col_name":["","\u0110\u00fang","Sai"],"arr_ques":["H\u00ecnh khai tri\u1ec3n m\u1eb7t xung quanh c\u1ee7a m\u1ed9t h\u00ecnh tr\u1ee5 l\u00e0 m\u1ed9t h\u00ecnh ch\u1eef nh\u1eadt","H\u00ecnh khai tri\u1ec3n m\u1eb7t xung quanh c\u1ee7a m\u1ed9t h\u00ecnh n\u00f3n l\u00e0 m\u1ed9t tam gi\u00e1c c\u00e2n"],"hint":"","explain":["\u0110\u00fang <br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D5.png' \/><\/center>","<br\/>Sai v\u00ec h\u00ecnh khai tri\u1ec3n m\u1eb7t xung quanh c\u1ee7a m\u1ed9t h\u00ecnh n\u00f3n l\u00e0 m\u1ed9t h\u00ecnh qu\u1ea1t.<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D2.png' \/><\/center> "]}]}],"id_ques":1692},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<span class='basic_left'>Di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n c\u1ee7a h\u00ecnh n\u00f3n c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y l\u00e0 $r,$ \u0111\u01b0\u1eddng sinh $l$ v\u00e0 chi\u1ec1u cao $h$ \u0111\u01b0\u1ee3c t\u00ednh b\u1eb1ng c\u00f4ng th\u1ee9c ","select":["A. ${{S}_{tp}}=\\pi rl+2\\pi {{r}^{2}}$ ","B. ${{S}_{tp}}=\\pi rl+\\pi {{r}^{2}}$ ","C. ${{S}_{tp}}=2\\pi rl+2\\pi {{r}^{2}}$ "],"hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D1.png' \/><\/center><br\/><br\/>Di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n c\u1ee7a h\u00ecnh n\u00f3n b\u1eb1ng di\u1ec7n t\u00edch xung quanh h\u00ecnh n\u00f3n c\u1ed9ng v\u1edbi di\u1ec7n t\u00edch \u0111\u00e1y:<br\/>${{S}_{tp}}=\\pi rl+\\pi {{r}^{2}}$<br\/>Trong \u0111\u00f3 <br\/>$r:$ B\u00e1n k\u00ednh \u0111\u00e1y<br\/>$l:$ \u0110\u01b0\u1eddng sinh<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span> <\/span>","column":3}]}],"id_ques":1693},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh n\u00f3n c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y $r,$ \u0111\u01b0\u1eddng sinh $l$ v\u00e0 \u0111\u01b0\u1eddng cao $h.$ Khai tri\u1ec3n m\u1eb7t xung quanh c\u1ee7a h\u00ecnh n\u00f3n, ta \u0111\u01b0\u1ee3c m\u1ed9t h\u00ecnh qu\u1ea1t. Khi \u0111\u00f3 s\u1ed1 \u0111o cung c\u1ee7a h\u00ecnh qu\u1ea1t theo $r $ v\u00e0 $l$ l\u00e0:","select":["A. $\\dfrac{r}{l}{{.180}^{o}}$ ","B. $\\dfrac{r}{h}{{.360}^{o}}$ ","C. $\\dfrac{r}{l}{{.360}^{o}}$ "],"hint":"Chu vi \u0111\u00e1y h\u00ecnh n\u00f3n b\u1eb1ng \u0111\u1ed9 d\u00e0i cung c\u1ee7a h\u00ecnh qu\u1ea1t tr\u00f2n.","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D2a.png' \/><\/center><br\/><br\/>\u0110\u1ed9 d\u00e0i cung c\u1ee7a h\u00ecnh qu\u1ea1t tr\u00f2n l\u00e0 $\\dfrac{\\pi ln }{180}$ <br\/>M\u00e0 chu vi \u0111\u00e1y c\u1ee7a h\u00ecnh n\u00f3n (c\u0169ng l\u00e0 \u0111\u1ed9 d\u00e0i c\u1ee7a cung $AB$ c\u1ee7a h\u00ecnh qu\u1ea1t) l\u00e0: $2\\pi r$ <br\/>Suy ra $2\\pi r=\\dfrac{\\pi ln }{180}\\Leftrightarrow n=\\dfrac{2\\pi r.180}{\\pi l }=\\dfrac{r}{l}.360$<br\/>S\u1ed1 \u0111o cung $AB$ c\u1ee7a h\u00ecnh qu\u1ea1t l\u00e0 ${{n}^{o}}=\\dfrac{r}{l}{{.360}^{o}}$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span> <\/span>","column":3}]}],"id_ques":1694},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"<span class='basic_left'>H\u00ecnh khai tri\u1ec3n c\u1ee7a m\u1eb7t xung quanh c\u1ee7a m\u1ed9t h\u00ecnh n\u00f3n l\u00e0 m\u1ed9t h\u00ecnh qu\u1ea1t c\u00f3 s\u1ed1 \u0111o cung b\u1eb1ng ${{120}^{o}}$ nh\u01b0 h\u00ecnh v\u1ebd.<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D3.png' \/><\/center><br\/> T\u00ednh $tg\\alpha $","select":["A. $\\dfrac{\\sqrt{3}}{4}$ ","B. $\\dfrac{\\sqrt{2}}{2}$ ","C. $\\dfrac{\\sqrt{2}}{3}$ ","D. $\\dfrac{\\sqrt{2}}{4}$"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>+ B\u01b0\u1edbc 1: \u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c s\u1ed1 \u0111o cung h\u00ecnh qu\u1ea1t ${{n}^{o}}=\\dfrac{r}{l}{{.360}^{o}}$, ta t\u00ecm $\\dfrac{r}{l}$ <br\/>+B\u01b0\u1edbc 2: Bi\u1ec3u di\u1ec5n $l$ qua $r.$ T\u1eeb \u0111\u00f3 t\u00ecm $h$<br\/>+ B\u01b0\u1edbc 3: T\u00ednh $tg\\alpha =\\dfrac{r}{h}$<br\/><br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D3.png' \/><\/center><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>S\u1ed1 \u0111o cung h\u00ecnh qu\u1ea1t b\u1eb1ng ${{120}^{o}}$ n\u00ean ta c\u00f3 $\\dfrac{r}{l}{{.360}^{o}}={{120}^{o}}\\Leftrightarrow \\dfrac{r}{l}=\\dfrac{1}{3}$<br\/>Suy ra $l=3r$ <br\/>Tam gi\u00e1c $SOA$ vu\u00f4ng t\u1ea1i $O.$ \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago, ta c\u00f3:<br\/>${{l}^{2}}={{h}^{2}}+{{r}^{2}}$<br\/>$\\Rightarrow {{h}^{2}}={{l}^{2}}-{{r}^{2}}=9{{r}^{2}}-{{r}^{2}}=8{{r}^{2}}\\Rightarrow h=2\\sqrt{2}r$ <br\/>$\\Rightarrow tg\\alpha =\\dfrac{r}{h}=\\dfrac{r}{2\\sqrt{2}r}=\\dfrac{1}{2\\sqrt{2}}=\\dfrac{\\sqrt{2}}{4}$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span> <\/span>","column":4}]}],"id_ques":1695},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh n\u00f3n c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y b\u1eb1ng $7$ $cm,$ chi\u1ec1u cao b\u1eb1ng $24$ $cm.$<br\/><b>C\u00e2u a:<\/b> T\u00ednh s\u1ed1 \u0111o cung h\u00ecnh qu\u1ea1t khi khai tri\u1ec3n m\u1eb7t xung quanh c\u1ee7a h\u00ecnh n\u00f3n.","select":["A. ${{105}^{o}}$ ","B. ${{100}^{o}}48'$","C. ${{110}^{o}}48'$","D. ${{100}^{o}}$"],"hint":"\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh s\u1ed1 \u0111o cung h\u00ecnh qu\u1ea1t khi khai tri\u1ec3n m\u1eb7t xung quanh h\u00ecnh n\u00f3n:<br\/>${{n}^{o}}=\\dfrac{r}{l}{{.360}^{o}}$ ","explain":"<span class='basic_left'>\u0110\u1ed9 d\u00e0i \u0111\u01b0\u1eddng sinh c\u1ee7a h\u00ecnh n\u00f3n l\u00e0:<br\/>$l=\\sqrt{{{h}^{2}}+{{r}^{2}}}=\\sqrt{{{24}^{2}}+{{7}^{2}}}=\\sqrt{625}=25\\left( cm \\right)$ <br\/>S\u1ed1 \u0111o cung h\u00ecnh qu\u1ea1t khi khai tri\u1ec3n m\u1eb7t xung quanh h\u00ecnh n\u00f3n l\u00e0:<br\/> ${{n}^{o}}=\\dfrac{r}{l}{{.360}^{o}}=\\dfrac{7}{25}{{.360}^{o}}={{100}^{o}}48'$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span> <\/span>","column":4}]}],"id_ques":1696},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"fill_the_blank","correct":[[["549,5"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh n\u00f3n c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y b\u1eb1ng $7$ $cm,$ chi\u1ec1u cao b\u1eb1ng $24$ $cm.$<br\/><b>C\u00e2u b:<\/b> T\u00ednh di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh n\u00f3n (l\u1ea5y $\\pi =3,14$ ) <br\/><b>\u0110\u00e1p s\u1ed1: <\/b> _input_$(cm^2)$ <\/span>","hint":"\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch xung quanh: ${{S}_{xq}}=\\pi rl$ ","explain":"<span class='basic_left'>Theo <b>c\u00e2u a<\/b>, ta c\u00f3 $l=25\\left( cm \\right)$ <br\/>Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh n\u00f3n l\u00e0:<br\/>${{S}_{xq}}=\\pi rl=\\pi .7.25=3,14.7.25=549,5\\left( c{{m}^{2}} \\right)$ <br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $549,5.$<\/span><\/span>"}]}],"id_ques":1697},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"fill_the_blank","correct":[[["392"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh n\u00f3n c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y b\u1eb1ng $7$ $cm,$ chi\u1ec1u cao b\u1eb1ng $24$ $cm.$<br\/><b>C\u00e2u c:<\/b> T\u00ednh th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh n\u00f3n <br\/><b>\u0110\u00e1p s\u1ed1: <\/b> _input_$\\pi$$(cm^3)$ <\/span>","hint":"\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh th\u1ec3 t\u00edch: $V=\\dfrac{1}{3}\\pi {{r}^{2}}h.$","explain":"<span class='basic_left'>Th\u1ec3 t\u00edch h\u00ecnh n\u00f3n l\u00e0:<br\/> $V=\\dfrac{1}{3}\\pi {{r}^{2}}h=\\dfrac{1}{3}\\pi {{.7}^{2}}.24=392 \\pi$ $(cm^3)$ <br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $392.$<\/span><\/span>"}]}],"id_ques":1698},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["40"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh n\u00f3n c\u00f3 di\u1ec7n t\u00edch xung quanh b\u1eb1ng $960$ $cm^2,$ chu vi \u0111\u00e1y b\u1eb1ng $48$$cm.$ \u0110\u01b0\u1eddng sinh c\u1ee7a h\u00ecnh n\u00f3n \u0111\u00f3 b\u1eb1ng _input_$(cm)$ <\/span>","hint":"\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch xung quanh, ta gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh: ${{S}_{xq}}=960$ \u0111\u1ec3 t\u00ecm \u0111\u01b0\u1eddng sinh.","explain":"<span class='basic_left'>\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c ${{S}_{xq}}=\\pi rl=\\dfrac{2\\pi r}{2}l$ <br\/>Do ${{S}_{xq}}=960\\left( c{{m}^{2}} \\right)$ v\u00e0 chu vi \u0111\u00e1y $2\\pi r=48\\left( cm \\right)$ n\u00ean ta c\u00f3:<br\/>$960=\\dfrac{48}{2}.l\\Leftrightarrow l=40\\left( cm \\right)$ <br\/>V\u1eady \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng sinh c\u1ee7a h\u00ecnh n\u00f3n l\u00e0 $40$$cm$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $40.$<\/span><\/span>"}]}],"id_ques":1699},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["6"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh n\u00f3n c\u00f3 th\u1ec3 t\u00edch b\u1eb1ng $264$ $dm^3,$ chi\u1ec1u cao b\u1eb1ng $7$$dm.$ L\u1ea5y $\\pi =\\dfrac{22}{7}$ th\u00ec b\u00e1n k\u00ednh \u0111\u00e1y c\u1ee7a h\u00ecnh n\u00f3n \u0111\u00f3 b\u1eb1ng _input_ $(dm)$ <\/span>","hint":"\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh th\u1ec3 t\u00edch, gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh t\u00ecm $V=264$ \u0111\u1ec3 t\u00ecm b\u00e1n k\u00ednh.","explain":"<span class='basic_left'>\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c:<br\/>$V=\\dfrac{1}{3}\\pi {{r}^{2}}h$ <br\/>Thay $V=264,$ $\\pi =\\dfrac{22}{7}$ v\u00e0 $h=7$ v\u00e0o c\u00f4ng th\u1ee9c, ta c\u00f3:<br\/>$264=\\dfrac{1}{3}.\\dfrac{22}{7}.{{r}^{2}}.7\\Leftrightarrow {{r}^{2}}=36\\Leftrightarrow r=6$ $(dm)$<br\/>V\u1eady b\u00e1n k\u00ednh \u0111\u00e1y c\u1ee7a h\u00ecnh n\u00f3n l\u00e0 $6$ $dm$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $6.$<\/span><\/span>"}]}],"id_ques":1700},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh n\u00f3n c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y b\u1eb1ng $r,$ di\u1ec7n t\u00edch xung quanh g\u1ea5p \u0111\u00f4i di\u1ec7n t\u00edch \u0111\u00e1y. T\u00ednh th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh n\u00f3n theo $r$ ","select":["A. $V= \\dfrac{\\sqrt{3}}{2}\\pi {{r}^{3}}$","B. $V= \\dfrac{\\sqrt{3}}{3}\\pi {{r}^{3}}$","C. $V= \\sqrt{2}\\pi {r}^{3}$","D. $V= \\sqrt{3}\\pi {r}^{3}$"],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn<\/span><br\/>+ B\u01b0\u1edbc 1: T\u00ednh \u0111\u01b0\u1eddng sinh $l$ theo $r$<br\/>+ B\u01b0\u1edbc 2: \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago, t\u00ednh chi\u1ec1u cao $h$<br\/>+ B\u01b0\u1edbc 3: T\u00ednh th\u1ec3 t\u00edch h\u00ecnh n\u00f3n <br\/><span class='basic_green'>L\u1eddi gi\u1ea3i<\/span><br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D1.png' \/><\/center><br\/>Di\u1ec7n t\u00edch xung quanh g\u1ea5p \u0111\u00f4i di\u1ec7n t\u00edch \u0111\u00e1y n\u00ean ta c\u00f3:<br\/>$\\pi rl=2\\pi {{r}^{2}}\\Leftrightarrow l=2r$ <br\/>Ta c\u00f3 ${{r}^{2}}+{{h}^{2}}={{l}^{2}}$ (\u0111\u1ecbnh l\u00ed Pytago)<br\/>Suy ra:<br\/> ${{h}^{2}}={{l}^{2}}-{{r}^{2}}=\\left( 4{{r}^{2}} \\right)-{{r}^{2}}=3{{r}^{2}}\\Rightarrow h=\\sqrt{3}r$ <br\/>Th\u1ec3 t\u00edch h\u00ecnh n\u00f3n l\u00e0:<br\/> $V=\\dfrac{1}{3}\\pi {{r}^{2}}h=\\dfrac{1}{3}\\pi {{r}^{2}}.\\sqrt{3}r=\\dfrac{\\sqrt{3}}{3}\\pi {{r}^{3}}$ (\u0111\u01a1n v\u1ecb th\u1ec3 t\u00edch)<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span> <\/span>","column":2}]}],"id_ques":1701},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh n\u00f3n v\u00e0 m\u1ed9t h\u00ecnh tr\u1ee5 c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y b\u1eb1ng nhau v\u00e0 chi\u1ec1u cao b\u1eb1ng nhau. T\u1ec9 s\u1ed1 c\u00e1c th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh tr\u1ee5 v\u00e0 h\u00ecnh n\u00f3n b\u1eb1ng:","select":["A. $1$","B. $3$","C. $\\dfrac{1}{2}$","D. $\\dfrac{2}{3}$"],"hint":"","explain":"<span class='basic_left'>Gi\u1ea3 s\u1eed h\u00ecnh n\u00f3n v\u00e0 h\u00ecnh tr\u1ee5 c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y l\u00e0 $r$ v\u00e0 chi\u1ec1u cao $h. $ Ta c\u00f3<br\/>+ Th\u1ec3 t\u00edch h\u00ecnh tr\u1ee5 l\u00e0 ${{V}_{T}}=\\pi {{r}^{2}}h$ <br\/>+ Th\u1ec3 t\u00edch h\u00ecnh n\u00f3n l\u00e0 ${{V}_{N}}=\\dfrac{1}{3}\\pi {{r}^{2}}h$ <br\/>Ta c\u00f3:<br\/> $\\dfrac{{{V}_{T}}}{{{V}_{N}}}=\\dfrac{\\pi {{r}^{2}}h}{\\dfrac{1}{3}\\pi {{r}^{2}}h}=3$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span> <\/span>","column":2}]}],"id_ques":1702},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o c\u00e1c ch\u1ed7 tr\u1ed1ng theo h\u00ecnh v\u1ebd sau","title_trans":"","temp":"fill_the_blank","correct":[[["4"],["5"],["20"],["36"],["16"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","ques":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D4.png' \/><\/center><br\/><table><tr><td>B\u00e1n k\u00ednh \u0111\u00e1y <br\/>$r\\,(cm)$<\/td><td>\u0110\u01b0\u1eddng k\u00ednh \u0111\u00e1y <br\/>$d\\,(cm)$<\/td><td>\u0110\u1ed9 d\u00e0i \u0111\u01b0\u1eddng sinh<br\/>$l\\,(cm)$<\/td><td>Chi\u1ec1u cao<br\/>$h\\,(cm)$<\/td><td>Di\u1ec7n t\u00edch xung quanh<br\/>$S_{xq}\\,(cm^2)$<\/td><td>Di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n<br\/>$S_{tp}\\,(cm^2)$<\/td><td>Th\u1ec3 t\u00edch<br\/>$V\\,(cm^3)$<\/td><\/tr><tr><td>_input_<\/td><td>$8$<\/td><td>_input_<\/td><td>$3$<\/td><td>_input_$\\pi$<\/td><td>_input_$\\pi$<\/td><td>_input_$\\pi$<\/td><\/tr><\/table><\/span>","hint":"","explain":"<span class='basic_left'>V\u00ec \u0111\u01b0\u1eddng k\u00ednh $d=8$ $(cm)$ n\u00ean b\u00e1n k\u00ednh \u0111\u00e1y $r=\\dfrac{d}{2}=\\dfrac{8}{2}=4\\left( cm \\right)$ <br\/>\u0110\u1ed9 d\u00e0i \u0111\u01b0\u1eddng sinh $l=\\sqrt{{{r}^{2}}+{{h}^{2}}}=\\sqrt{{{4}^{2}}+{{3}^{2}}}=\\sqrt{25}=5$ $(cm)$<br\/>Di\u1ec7n t\u00edch xung quanh: ${{S}_{xq}}=\\pi rl=\\pi .4.5=20\\pi $ $(cm^2)$<br\/>Di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n: ${{S}_{tp}}=\\pi rl+\\pi {{r}^{2}}=20\\pi +16\\pi =36\\pi $ $(cm^2)$<br\/>Th\u1ec3 t\u00edch: $V=\\dfrac{1}{3}\\pi {{r}^{2}}h=\\dfrac{1}{3}.\\pi {{.4}^{2}}.3=16\\pi $ $(cm^3)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u1ea7n l\u01b0\u1ee3t t\u1eeb tr\u00e1i sang ph\u1ea3i l\u00e0 $4;$$5;$$ 20;$ $36;$$16.$ <\/span><\/span>"}]}],"id_ques":1703},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o c\u00e1c ch\u1ed7 tr\u1ed1ng theo h\u00ecnh v\u1ebd sau","title_trans":"L\u00e0m tr\u00f2n k\u1ebft qu\u1ea3 \u0111\u1ebfn s\u1ed1 th\u1eadp ph\u00e2n th\u1ee9 nh\u1ea5t","temp":"fill_the_blank","correct":[[["10"],["6,9"],["4,8"],["108,4","108,3"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","ques":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D4.png' \/><\/center><br\/><table><tr><td>B\u00e1n k\u00ednh \u0111\u00e1y <br\/>$r\\,(cm)$<\/td><td>\u0110\u01b0\u1eddng k\u00ednh \u0111\u00e1y <br\/>$d\\,(cm)$<\/td><td>\u0110\u1ed9 d\u00e0i \u0111\u01b0\u1eddng sinh<br\/>$l\\,(cm)$<\/td><td>Chi\u1ec1u cao<br\/>$h\\,(cm)$<\/td><td>Di\u1ec7n t\u00edch xung quanh<br\/>$S_{xq}\\,(cm^2)$<\/td><td>Th\u1ec3 t\u00edch<br\/>$V\\,(cm^3)$<\/td><\/tr><tr><td>$5$<\/td><td>_input_<\/td><td>_input_<\/td><td>_input_<\/td><td>_input_<\/td><td>$125$<\/td><\/tr><\/table><\/span>","hint":"","explain":"<span class='basic_left'>B\u00e1n k\u00ednh \u0111\u00e1y b\u1eb1ng $5$$cm$ n\u00ean \u0111\u01b0\u1eddng k\u00ednh \u0111\u00e1y $ d=2.5=10$$(cm)$<br\/>V\u00ec th\u1ec3 t\u00edch $V=125\\left( c{{m}^{3}} \\right)$ v\u00e0 b\u00e1n k\u00ednh \u0111\u00e1y l\u00e0 $5$ $cm$ n\u00ean $\\dfrac{1}{3}.\\pi {{.5}^{2}}.h=125\\Leftrightarrow h=\\dfrac{15}{\\pi }\\approx 4,8$ $(cm) $<br\/>\u0110\u01b0\u1eddng sinh: $l=\\sqrt{{{h}^{2}}+{{r}^{2}}}=\\sqrt{{{\\left( \\dfrac{15}{\\pi } \\right)}^{2}}+{{5}^{2}}}\\approx 6,9\\left( cm \\right)$ <br\/>Di\u1ec7n t\u00edch xung quanh: ${{S}_{xq}}=\\pi rl = \\pi .5.6,9\\approx 108,4$ $(cm^2)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u1ea7n l\u01b0\u1ee3t t\u1eeb tr\u00e1i sang ph\u1ea3i l\u00e0 $10;$$6,9;$$4,8;$$ 108,4.$ <\/span><\/span>"}]}],"id_ques":1704},{"time":24,"part":[{"title":"Kh\u1eb3ng \u0111\u1ecbnh \u0111\u00fang hay sai","title_trans":"Cho h\u00ecnh n\u00f3n c\u1ee5t c\u00f3 ${{r}_{1}};{{r}_{2}}$ l\u00e0 b\u00e1n k\u00ednh \u0111\u00e1y, $l$ l\u00e0 \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng sinh, $h$ l\u00e0 chi\u1ec1u cao. K\u00ed hi\u1ec7u ${{S}_{xq}}$ l\u00e0 di\u1ec7n t\u00edch xung quanh, $V$ l\u00e0 th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh n\u00f3n c\u1ee5t.<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D7.png' \/><\/center>","temp":"true_false","correct":[["f","t","t","f"]],"list":[{"point":5,"image":"","col_name":["","\u0110\u00fang","Sai"],"arr_ques":["${{S}_{xq}}=\\pi \\left( {{r}_{1}}+{{r}_{2}} \\right)h$ ","${{S}_{xq}}=\\pi \\left( {{r}_{1}}+{{r}_{2}} \\right)l$","$V=\\dfrac{1}{3}\\pi h\\left( r_{1}^{2}+r_{2}^{2}+{{r}_{1}}{{r}_{2}} \\right)$ ","$V=\\dfrac{1}{3}\\pi h\\left( r_{1}^{2}+r_{2}^{2}-{{r}_{1}}{{r}_{2}} \\right)$"],"hint":"","explain":["Sai v\u00ec ${{S}_{xq}}=\\pi \\left( {{r}_{1}}+{{r}_{2}} \\right)l$","<br\/>\u0110\u00fang","<br\/>\u0110\u00fang","<br\/>Sai v\u00ec $V=\\dfrac{1}{3}\\pi h\\left( r_{1}^{2}+r_{2}^{2}+{{r}_{1}}{{r}_{2}} \\right)$ "]}]}],"id_ques":1705},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["316"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","ques":"<span class='basic_left'>T\u00ednh th\u1ec3 t\u00edch c\u1ee7a m\u1ed9t h\u00ecnh n\u00f3n c\u1ee5t c\u00f3 c\u00e1c b\u00e1n k\u00ednh \u0111\u00e1y b\u1eb1ng $3$ $cm$ v\u00e0 $7$ $cm,$ chi\u1ec1u cao b\u1eb1ng $12$$cm.$<br\/><b> \u0110\u00e1p s\u1ed1: <\/b>_input_$\\pi\\,(cm^3)$ <\/span>","hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D7.png' \/><\/center><br\/>Th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh n\u00f3n l\u00e0 $V=\\dfrac{1}{3}\\pi \\left( r_{1}^{2}+r_{2}^{2}+{{r}_{1}}{{r}_{2}} \\right)h=\\dfrac{1}{3}\\pi \\left( {{3}^{2}}+{{7}^{2}}+3.7 \\right).12=316\\pi \\left( c{{m}^{3}} \\right)$ <br\/> <span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $316$<\/span><\/span>"}]}],"id_ques":1706},{"time":24,"part":[{"title":"Ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"<span class='basic_left'>T\u00ednh \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng sinh c\u1ee7a m\u1ed9t h\u00ecnh n\u00f3n c\u1ee5t c\u00f3 c\u00e1c b\u00e1n k\u00ednh \u0111\u00e1y b\u1eb1ng ${{r}_{1}};{{r}_{2}}$, chi\u1ec1u cao b\u1eb1ng $h.$<\/span>","select":["A. $l=\\sqrt{{{h}^{2}}+{{\\left( {{r}_{1}}-{{r}_{2}} \\right)}^{2}}}$ ","B. $l=\\sqrt{{{h}^{2}}+{{\\left( {{r}_{1}}+{{r}_{2}} \\right)}^{2}}}$ ","C. $l=\\sqrt{{{h}^{2}}+{{\\left( {{r}_{2}}-{{r}_{1}} \\right)}^{2}}}$ ","D. $l=\\sqrt{{{h}^{2}}-{{\\left( {{r}_{2}}-{{r}_{1}} \\right)}^{2}}}$ "],"hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D6.png' \/><\/center><br\/><br\/>H\u1ea1 $AH$ vu\u00f4ng g\u00f3c v\u1edbi $O\u2019B.$<br\/>D\u1ec5 th\u1ea5y $AOO\u2019H$ l\u00e0 h\u00ecnh ch\u1eef nh\u1eadt n\u00ean $O\u2019H=AO=r_1$<br\/>Suy ra $BH=r_2-r_1$<br\/>$\\Delta AHB$ vu\u00f4ng t\u1ea1i $H.$ \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago, ta c\u00f3:<br\/>$A{{B}^{2}}=A{{H}^{2}}+B{{H}^{2}}={{h}^{2}}+{{\\left( {{r}_{2}}-{{r}_{1}} \\right)}^{2}}\\Rightarrow l=AB=\\sqrt{{{h}^{2}}+{{\\left( {{r}_{2}}-{{r}_{1}} \\right)}^{2}}}$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C<\/span><\/span>","column":2}]}],"id_ques":1707},{"time":24,"part":[{"title":"Ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"<span class='basic_left'>T\u00ednh di\u1ec7n t\u00edch xung quanh c\u1ee7a m\u1ed9t h\u00ecnh n\u00f3n c\u1ee5t c\u00f3 c\u00e1c b\u00e1n k\u00ednh \u0111\u00e1y b\u1eb1ng $3$ $cm$ v\u00e0 $7$ $cm,$ chi\u1ec1u cao b\u1eb1ng $3$$cm.$<\/span>","select":["A. ${{S}_{xq}}=20\\pi$ $(cm^2)$ ","B. ${{S}_{xq}}=30\\pi$ $(cm^2)$ ","C. ${{S}_{xq}}=12\\pi$ $(cm^2)$ ","D. ${{S}_{xq}}=50\\pi$ $(cm^2)$ "],"hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>B\u01b0\u1edbc 1: \u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng sinh: $l=\\sqrt{{{h}^{2}}+{{\\left( {{r}_{2}}-{{r}_{1}} \\right)}^{2}}}$ \u0111\u1ec3 t\u00ecm $l$<br\/>B\u01b0\u1edbc 2: \u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch xung quanh: ${{S}_{xq}}=\\pi \\left( {{r}_{1}}+{{r}_{2}} \\right)l$ \u0111\u1ec3 t\u00ednh di\u1ec7n t\u00edch.<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span> <br\/>Ta c\u00f3 \u0111\u01b0\u1eddng sinh $l=\\sqrt{{{h}^{2}}+{{\\left( {{r}_{2}}-{{r}_{1}} \\right)}^{2}}}=\\sqrt{{{3}^{2}}+{{\\left( 7-3 \\right)}^{2}}}=\\sqrt{25}=5$ <br\/>Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh n\u00f3n l\u00e0 ${{S}_{xq}}=\\pi \\left( {{r}_{1}}+{{r}_{2}} \\right)l=\\pi \\left( 3+7 \\right).5=50\\pi $ $(cm^2)$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D<\/span><\/span>","column":2}]}],"id_ques":1708},{"time":24,"part":[{"title":"Ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"<span class='basic_left'>Cho h\u00ecnh v\u1ebd: <br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D8.png' \/><\/center><br\/>Khi quay h\u00ecnh quanh c\u1ea1nh $AD$ th\u00ec t\u1ea1o ra:<\/span>","select":["A. M\u1ed9t h\u00ecnh tr\u1ee5 ","B. M\u1ed9t h\u00ecnh n\u00f3n ","C. Hai h\u00ecnh n\u00f3n","D. M\u1ed9t h\u00ecnh n\u00f3n c\u1ee5t"],"hint":"","explain":"<span class='basic_left'>Khi quay h\u00ecnh quanh c\u1ea1nh $AD,$ ta \u0111\u01b0\u1ee3c hai h\u00ecnh n\u00f3n:<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai23/lv1/img\/H942_D10.png' \/><\/center><br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n ch\u1ecdn l\u00e0 C<\/span><\/span>","column":2}]}],"id_ques":1709},{"time":24,"part":[{"title":"Ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<span class='basic_left'>T\u00ednh di\u1ec7n t\u00edch c\u1ea7n s\u01a1n c\u1ea3 m\u1eb7t ngo\u00e0i v\u00e0 m\u1eb7t trong m\u1ed9t chi\u1ebfc x\u00f4 h\u00ecnh n\u00f3n c\u1ee5t (kh\u00f4ng c\u00f3 n\u1eafp) c\u00f3 \u0111\u01b0\u1eddng sinh $4$ $dm,$ \u0111\u01b0\u1eddng k\u00ednh \u0111\u00e1y x\u00f4 $3$ $dm,$ \u0111\u01b0\u1eddng k\u00ednh mi\u1ec7ng x\u00f4 $4$ $dm.$<\/span>","select":["A. $16,25\\pi $$dm^2$ ","B. $32,5\\pi $$dm^2$","C. $18,5\\pi $$dm^2$","D. $30,25\\pi $$dm^2$"],"hint":"Di\u1ec7n t\u00edch c\u1ea7n s\u01a1n b\u1eb1ng $2.$(di\u1ec7n t\u00edch xung quanh $+$ di\u1ec7n t\u00edch \u0111\u00e1y x\u00f4) v\u00ec g\u1ed3m c\u1ea3 m\u1eb7t ngo\u00e0i v\u00e0 m\u1eb7t trong.","explain":"<span class='basic_left'>B\u00e1n k\u00ednh \u0111\u00e1y x\u00f4 l\u00e0 $r_1=1,5$ $dm,$ b\u00e1n k\u00ednh mi\u1ec7ng x\u00f4 l\u00e0 $r_2=2$$dm$<br\/>Di\u1ec7n t\u00edch xung quanh x\u00f4 l\u00e0: ${{S}_{xq}}=\\pi \\left( {{r}_{1}}+{{r}_{2}} \\right)l=\\pi \\left( 1,5+2 \\right).4=14\\pi \\left( d{{m}^{2}} \\right)$ <br\/>Di\u1ec7n t\u00edch \u0111\u00e1y x\u00f4 l\u00e0 ${{S}_{\u0111}}=\\pi r_{1}^{2}=\\pi .1,{{5}^{2}}=2,25\\pi \\left( d{{m}^{2}} \\right)$ <br\/>Di\u1ec7n t\u00edch c\u1ea7n s\u01a1n l\u00e0:<br\/>$S=2\\left( {{S}_{xq}}+{{S}_{\u0111}} \\right)=2\\left( 14\\pi +2,25\\pi \\right)=32,5\\pi \\left( d{{m}^{2}} \\right)$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n ch\u1ecdn l\u00e0 B.<\/span><\/span>","column":2}]}],"id_ques":1710}],"lesson":{"save":0,"level":1}}