{"segment":[{"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":"Gi\u1ea3i tam gi\u00e1c vu\u00f4ng $ABC$, bi\u1ebft $\\widehat{A}=90^o$ v\u00e0 $a=72 cm$; $\\widehat{B}=58^o$. ","select":["A. $\\widehat{C}=32^o;$$ b\\approx 38\\,cm;\\, c\\approx 61\\,cm$","B. $\\widehat{C}=32^o;$$ b\\approx 61\\,cm;\\, c\\approx 38\\,cm$","C. $\\widehat{C}=32^o;$$ b\\approx 65\\,cm;\\, c\\approx 42\\,cm$","D. $\\widehat{C}=32^o;$$ b\\approx 42\\,cm;\\, c\\approx 65\\,cm$"],"explain":" <span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D26.png' \/><\/center><br\/>X\u00e9t $\\Delta ABC$ c\u00f3: $ \\widehat{A}=90^o$<br\/>$\\Rightarrow \\widehat{C}=90^o-\\widehat{B}$$=90^o-58^o=32^o$($\\widehat C$ v\u00e0 $\\widehat B$ l\u00e0 hai g\u00f3c ph\u1ee5 nhau)<br\/>\u00c1p d\u1ee5ng h\u1ec7 th\u1ee9c li\u00ean h\u1ec7 gi\u1eefa c\u1ea1nh v\u00e0 g\u00f3c trong tam gi\u00e1c vu\u00f4ng ta c\u00f3: <br\/>$b=a.\\sin B$$=72.\\sin58^o \\approx 61 \\,(cm)$<br\/>$c=a.\\sin C$$=72.\\sin32^o \\approx 38 \\,(cm)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B<\/span><\/span>","column":1}]}],"id_ques":1371},{"time":24,"part":[{"title":"Ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"select":["A. $\\dfrac{1}{3}$","B. $\\dfrac{2}{3}$","C. $\\dfrac{4}{3}$"],"ques":"Cho $tg\\, \\alpha =3$, khi \u0111\u00f3 $cotg\\, \\alpha=$?","hint":"V\u1eadn d\u1ee5ng c\u00f4ng th\u1ee9c: $\\tan \\alpha.cot\\alpha =1$","explain":"Ta c\u00f3: <br\/> $\\,\\,\\,\\,tg\\, \\alpha .cotg\\, \\alpha=1\\\\ \\Rightarrow 3.cotg\\,\\alpha =1\\\\ \\Rightarrow cotg\\,\\alpha =\\dfrac{1}{3}$"}]}],"id_ques":1372},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["23"]]],"list":[{"point":5,"width":60,"content":"","type_input":"","type_check":"","ques":"Cho tam gi\u00e1c $ABC$ vu\u00f4ng t\u1ea1i $A$ c\u00f3 $AB=21 cm$, $\\widehat{C}=40^o$, ph\u00e2n gi\u00e1c $BD$ ($D$ thu\u1ed9c $AC$).<br\/>\u0110\u1ed9 d\u00e0i ph\u00e2n gi\u00e1c $BD$ l\u00e0_input_ $(cm)$<br\/>(K\u1ebft qu\u1ea3 l\u00e0m tr\u00f2n \u0111\u1ebfn ch\u1eef s\u1ed1 h\u00e0ng \u0111\u01a1n v\u1ecb)","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D19.png' \/><\/center><br\/>X\u00e9t $\\Delta ABC$ c\u00f3: $ \\widehat{A}=90^o $<br\/>$\\Rightarrow \\widehat{B}=90^o-\\widehat{C}=90^o-40^o=50^o$ ($\\widehat C$ v\u00e0 $\\widehat B$ l\u00e0 hai g\u00f3c ph\u1ee5 nhau)<br\/>X\u00e9t tam gi\u00e1c $ABD$ vu\u00f4ng t\u1ea1i $A$. \u00c1p d\u1ee5ng t\u1ec9 s\u1ed1 l\u01b0\u1ee3ng gi\u00e1c ta c\u00f3: <br\/>$cos \\,\\widehat{\\dfrac{B}{2}}=\\cos \\widehat{ABD}=\\dfrac{AB}{BD}\\\\ \\Rightarrow BD=\\dfrac{21}{cos \\,\\widehat{\\dfrac{B}{2}}}=\\dfrac{21}{\\cos 25^o}\\approx 23\\,(cm)$<br\/><span class='basic_pink'>V\u1eady k\u1ebft qu\u1ea3 c\u1ea7n \u0111i\u1ec1n l\u00e0 $23$<\/span><\/span>"}]}],"id_ques":1373},{"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":"Cho tam gi\u00e1c $ABC$ vu\u00f4ng t\u1ea1i $A$, c\u00f3 $AC= 15, BC=17$. Khi \u0111\u00f3 tg $B$ b\u1eb1ng: ","select":["A. $\\dfrac{15}{17}$","B. $\\dfrac{8}{15}$","C. $\\dfrac{8}{17}$","D. $\\dfrac{15}{8}$"],"explain":" <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D23.png' \/><\/center><br\/>X\u00e9t $\\Delta ABC$ c\u00f3: $ \\widehat{A}=90^o$. \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00ed Pytago ta c\u00f3: <br\/>$BC^2=AB^2+AC^2\\\\ \\Rightarrow AB^2=17^2-15^2\\\\ \\Rightarrow AB^2=64 \\\\ \\Rightarrow AB = 8 $<br\/>$ \\tan B =\\dfrac{AC}{AB}=\\dfrac{15}{8}$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D<\/span>","column":4}]}],"id_ques":1374},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"<span class='basic_left'>Trong h\u00ecnh 1, $AC= 8 cm$, $AD= 9,6 cm$, $\\widehat{ABC}=90^o$, $\\widehat{ACB}=54^o$, v\u00e0 $\\widehat{ACD}=74^o$. <br\/><b> C\u00e2u 1: <\/b> \u0110\u1ed9 d\u00e0i \u0111o\u1ea1n th\u1eb3ng AB x\u1ea5p x\u1ec9 b\u1eb1ng <br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D21a.png' \/><\/center><\/span>","select":["A. $4,7 cm$","B. $5,32 cm$","C. $6,47 cm$","D. $6,89 cm$"],"explain":" <span class='basic_left'>X\u00e9t $\\Delta ABC$ c\u00f3: $\\widehat{B}=90^o$.<br\/> \u00c1p d\u1ee5ng h\u1ec7 th\u1ee9c v\u1ec1 c\u1ea1nh v\u00e0 g\u00f3c trong tam gi\u00e1c vu\u00f4ng ta c\u00f3: <br\/>$AB=AC.\\sin \\widehat{ACB}\\\\ \\Rightarrow AB =8.\\sin 54^o\\\\ \\Rightarrow AB \\approx 6,47 \\,(cm)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C<\/span><\/span>","column":4}]}],"id_ques":1375},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["53"]]],"list":[{"point":5,"width":80,"content":"","type_input":"","type_check":"","ques":"<span class='basic_left'>Trong h\u00ecnh 1, $AC= 8 cm$, $AD= 9,6 cm$, $\\widehat{ABC}=90^o$, $\\widehat{ACB}=54^o$, v\u00e0 $\\widehat{ACD}=74^o$. <br\/><b> C\u00e2u 2: <\/b> S\u1ed1 \u0111o $\\widehat{ADC}\\approx $_input_ $^o$<br\/>(K\u1ebft qu\u1ea3 l\u00e0m tr\u00f2n \u0111\u1ebfn \u0111\u1ed9) <br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D21a.png' \/><\/center><\/span>","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D21.png' \/><\/center><br\/>K\u1ebb $AH \\bot CD$ t\u1ea1i $H$<br\/>X\u00e9t $\\Delta ACH$ c\u00f3: $ \\widehat{H}=90^o$ <br\/> $ \\Rightarrow AH=AC.\\sin\\widehat{ACH}\\\\ \\Rightarrow AH = 8.\\sin 74^o \\approx 7,69 $<br\/>X\u00e9t $ \\Delta AHD$ c\u00f3: $ \\widehat{H}=90^o$ <br\/> $\\sin D=\\dfrac{AH}{AD}\\approx \\dfrac{7,69}{9,6}= 0,801 \\,(cm)\\\\ \\Rightarrow \\widehat{D}\\approx 53^o$<br\/><span class='basic_pink'>V\u1eady k\u1ebft qu\u1ea3 c\u1ea7n \u0111i\u1ec1n l\u00e0 $53$ <\/span><\/span>"}]}],"id_ques":1376},{"time":24,"part":[{"title":"H\u00e3y ch\u1ecdn \u0111\u00e1p \u00e1n Sai","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"X\u00e9t tam gi\u00e1c vu\u00f4ng $ABC$ v\u1edbi c\u00e1c y\u1ebfu t\u1ed1 \u0111\u01b0\u1ee3c cho trong h\u00ecnh 1. Ta c\u00f3<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D20.png' \/><\/center>","select":["A. $\\dfrac{a}{b}=\\dfrac{c}{h}$","B. $\\dfrac{a}{b}=\\dfrac{b}{b'}$","C. $\\dfrac{b}{c}=\\dfrac{b'}{c'}$","D. $\\dfrac{a}{c}=\\dfrac{c}{c'}$"],"explain":" <span class='basic_left'>Do $ah=bc$ n\u00ean $\\dfrac{a}{b}=\\dfrac{c}{h}$ $\\Rightarrow$ \u0110\u00e1p \u00e1n A \u0111\u00fang<br\/>Do $b^2=ab'$ n\u00ean $\\dfrac{a}{b}=\\dfrac{b}{b'}$ $\\Rightarrow$ \u0110\u00e1p \u00e1n B \u0111\u00fang <br\/> Do $c^2=ac'$ n\u00ean $\\dfrac{a}{c}=\\dfrac{c}{c'}$ $\\Rightarrow $ \u0110\u00e1p \u00e1n D \u0111\u00fang<br\/>Suy ra \u0111\u00e1p \u00e1n C sai<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C<\/span><\/span>","column":4}]}],"id_ques":1377},{"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'>T\u00ednh s\u1ed1 \u0111o c\u1ee7a g\u00f3c nh\u1ecdn $x$ bi\u1ebft:<br\/>$5tg\\, x -3cotg\\,(90^o-x)=2,46$(l\u00e0m tr\u00f2n \u0111\u1ebfn k\u1ebft qu\u1ea3 \u0111\u1ed9)<\/span>","select":["A. $x \\approx 48^o$","B. $x \\approx 51^o$","C. $x \\approx 54^o$","D. $x\\approx 57^o$"],"hint":"","explain":"<span class='basic_left'>Ta c\u00f3: <br\/>$5tg\\, -3cotg\\,(90^o-x)=2,46\\\\ \\Leftrightarrow 5tg\\, x- 3tg\\, x = 2,46\\\\ \\Leftrightarrow tg\\, x =1,23 \\\\ \\Leftrightarrow x \\approx 51^o$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B<\/span><\/span>","column":4}]}],"id_ques":1378},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["1"]]],"list":[{"point":5,"width":80,"content":"","type_input":"","type_check":"","ques":"Gi\u00e1 tr\u1ecb bi\u1ec3u th\u1ee9c: <br\/>$\\sin^4\\alpha+\\cos^4\\alpha+$$2\\sin^2\\alpha\\cos^2\\alpha=$_input_","hint":"D\u00f9ng h\u1eb1ng \u0111\u1eb3ng th\u1ee9c $(a+b)^2$ v\u00e0 \u00e1p d\u1ee5ng: $\\sin^2\\alpha+\\cos^2\\alpha=1$","explain":"<span class='basic_left'>Ta c\u00f3: <br\/>$\\,\\,\\,\\,$$\\sin^4\\alpha+\\cos^4\\alpha+$$2\\sin^2\\alpha\\cos^2\\alpha$<br\/>$=(\\sin^2\\alpha+\\cos^2\\alpha)^2\\\\=1$<br\/><span class='basic_pink'>V\u1eady k\u1ebft qu\u1ea3 c\u1ea7n \u0111i\u1ec1n l\u00e0 $1$<\/span><\/span>"}]}],"id_ques":1379},{"time":24,"part":[{"title":"\u0110i\u1ec1n d\u1ea5u $>, <, =$ th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["<"]]],"list":[{"point":5,"width":60,"content":"","type_input":"","type_check":"","ques":"So s\u00e1nh $cos\\, \\alpha$ _input_ $cotg\\,\\alpha$ (v\u1edbi $0^o < \\alpha < 90^o$)","hint":"$cotg\\,\\alpha=\\dfrac{cos\\, \\alpha}{sin\\, \\alpha}$","explain":"<span class='basic_left'> Ta c\u00f3: <br\/>V\u00ec $0^o < \\alpha < 90^o\\Rightarrow 0 < sin\\, \\alpha < 1$<br\/>Suy ra: $\\dfrac{cos\\, \\alpha}{1}<\\dfrac{cos\\, \\alpha}{sin\\, \\alpha}$ v\u00e0 <br\/>V\u1eady, $cos\\, \\alpha < cotg\\, \\alpha$<br\/><span class='basic_pink'>V\u1eady k\u1ebft qu\u1ea3 c\u1ea7n \u0111i\u1ec1n l\u00e0 $<$<\/span>"}]}],"id_ques":1380},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["11,76"]]],"list":[{"point":5,"width":80,"content":"","type_input":"","type_check":"","ques":"M\u1ed9t ng\u01b0\u1eddi quan s\u00e1t \u0111\u1ee9ng c\u00e1ch m\u1ed9t chi\u1ebfc th\u00e1p $10 m$, nh\u00ecn th\u1ea5y c\u00e1i th\u00e1p d\u01b0\u1edbi g\u00f3c $55^o$ v\u00e0 \u0111\u01b0\u1ee3c ph\u00e2n t\u00edch nh\u01b0 tr\u00ean h\u00ecnh 1. Chi\u1ec1u cao c\u1ee7a th\u00e1p l\u00e0:_input_ $(m)$<br\/>(K\u1ebft qu\u1ea3 l\u00e0m tr\u00f2n \u0111\u1ebfn s\u1ed1 th\u1eadp ph\u00e2n th\u1ee9 hai)<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D10.png' \/><\/center>","explain":"<span class='basic_left'><br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D11.png' \/><\/center><br\/>Ta c\u00f3 th\u1ec3 m\u00f4 t\u1ea3 l\u1ea1i b\u00e0i to\u00e1n b\u1eb1ng h\u00ecnh v\u1ebd nh\u01b0 tr\u00ean.<br\/> Khi \u0111\u00f3 chi\u1ec1u cao c\u1ee7a th\u00e1p l\u00e0 $BC$<br\/>X\u00e9t $\\Delta AHB$ c\u00f3: $\\widehat{H}=90^{o}$<br\/>\u00c1p d\u1ee5ng h\u1ec7 th\u1ee9c gi\u1eefa c\u1ea1nh v\u00e0 g\u00f3c trong tam gi\u00e1c vu\u00f4ng $ABH$, ta c\u00f3: <br\/>$HB=AH.tg\\,45^o$$=10.1=10 (m)$<br\/>X\u00e9t $ \\Delta AHC$ c\u00f3: $ \\widehat{H}=90^{o}$<br\/>\u00c1p d\u1ee5ng h\u1ec7 th\u1ee9c gi\u1eefa c\u1ea1nh v\u00e0 g\u00f3c trong tam gi\u00e1c vu\u00f4ng $ACH$, ta c\u00f3: <br\/>$HC=AH.tg\\,10^o $$\\approx 10.0,176 \\approx 1,76$<br\/>Chi\u1ec1u cao c\u1ee7a th\u00e1p l\u00e0:<br\/> $BC=CH+HB $$\\approx 10+1,76= 11,76 (m)$<br\/><span class='basic_pink'>V\u1eady k\u1ebft qu\u1ea3 c\u1ea7n \u0111i\u1ec1n l\u00e0 $11,76$ <\/span><\/span><\/span>"}]}],"id_ques":1381},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["24"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","type_check":"","ques":"C\u1ea1nh b\u00ean c\u1ee7a m\u1ed9t tam gi\u00e1c c\u00e2n d\u00e0i $17,2 cm$, g\u00f3c \u1edf \u0111\u00e1y l\u00e0 $46^o$<br\/>\u0110\u1ed9 d\u00e0i c\u1ea1nh \u0111\u00e1y c\u1ee7a tam gi\u00e1c c\u00e2n l\u00e0:_input_cm<br\/>(K\u1ebft qu\u1ea3 l\u00e0m tr\u00f2n \u0111\u1ebfn h\u00e0ng \u0111\u01a1n v\u1ecb)","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D9.png' \/><\/center><br\/>Gi\u1ea3 s\u1eed $\\Delta ABC$ c\u00e2n t\u1ea1i $A$ ; $AB=17,2 cm$ v\u00e0 $\\widehat{B}=46^o$<br\/>K\u1ebb $BH \\bot BC$ $\\Rightarrow BH=\\dfrac{1}{2}BC$ (t\u00ednh ch\u1ea5t)<br\/>X\u00e9t $\\Delta AHB$ c\u00f3: $\\widehat{H}=90^o $<br\/>\u00c1p d\u1ee5ng h\u1ec7 th\u1ee9c li\u00ean h\u1ec7 gi\u1eefa c\u1ea1nh v\u00e0 g\u00f3c trong tam gi\u00e1c vu\u00f4ng, ta c\u00f3: <br\/>$BH=AB.cos B$$=17,2.cos 46^o \\approx 12 (cm)$<br\/> Suy ra: $BC=2BH \\approx 24 (cm)$<br\/><span class='basic_pink'>V\u1eady k\u1ebft qu\u1ea3 c\u1ea7n \u0111i\u1ec1n l\u00e0 $24$<\/span><\/span>"}]}],"id_ques":1382},{"time":24,"part":[{"title":"Ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"select":["A. $\\dfrac{25}{8}$","B. $\\dfrac{22}{8}$","C. $\\dfrac{20}{8}$"],"ques":"<span class='basic_left'>Cho h\u00ecnh v\u1ebd, t\u00ecm $x$.<\/span><br\/><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D8.png' \/><\/center><br\/>\u0110\u00e1p s\u1ed1: $x=$?","explain":"\u00c1p d\u1ee5ng h\u1ec7 th\u1ee9c $b^2=ab'; \\,c^2=a.c'$ ta c\u00f3: <br\/>$5^2=x.8\\Rightarrow x=\\dfrac{25}{8}$"}]}],"id_ques":1383},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["12"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","type_check":"","ques":"Tam gi\u00e1c $ABC$ vu\u00f4ng t\u1ea1i$ A$ c\u00f3 \u0111\u01b0\u1eddng cao $AH$. Bi\u1ebft $BH= 8cm$, $CH= 18 cm$ <br\/>\u0110\u1ed9 d\u00e0i \u0111\u01b0\u1eddng cao $AH$ l\u00e0:_input_","hint":"Trong m\u1ed9t tam gi\u00e1c vu\u00f4ng, b\u00ecnh ph\u01b0\u01a1ng \u0111\u01b0\u1eddng cao \u1ee9ng v\u1edbi c\u1ea1nh huy\u1ec1n b\u1eb1ng t\u00edch hai h\u00ecnh chi\u1ebfu c\u1ee7a hai c\u1ea1nh g\u00f3c vu\u00f4ng tr\u00ean c\u1ea1nh huy\u1ec1n","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D7.png' \/><\/center><br\/>X\u00e9t $\\Delta ABC$ c\u00f3: $ \\widehat{A}=90^o; AH\\bot BC$<br\/>\u00c1p d\u1ee5ng h\u1ec7 th\u1ee9c v\u1ec1 c\u1ea1nh v\u00e0 \u0111\u01b0\u1eddng cao trong tam gi\u00e1c, ta c\u00f3: <br\/>$AH^2=BH.HC$$=8.18=144$$\\Rightarrow AH= 12\\,(cm)$<br\/><span class='basic_pink'>V\u1eady k\u1ebft qu\u1ea3 c\u1ea7n \u0111i\u1ec1n l\u00e0 $12$<\/span><\/span>"}]}],"id_ques":1384},{"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":"H\u00ecnh v\u1ebd d\u1ef1ng g\u00f3c $\\alpha$ sao cho $tg\\, \\alpha=\\dfrac{2}{5}$ l\u00e0:<br\/><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D6a.png' \/><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D6b.png' \/> ","select":["A. H\u00ecnh 1","B. H\u00ecnh 2","C. H\u00ecnh 3"],"explain":" <span class='basic_left'>D\u1ef1ng g\u00f3c vu\u00f4ng $xOy$. L\u1ea5y m\u1ed9t \u0111o\u1ea1n th\u1eb3ng l\u00e0m \u0111\u01a1n v\u1ecb. <br\/> Tr\u00ean tia $Ox$ l\u1ea5y \u0111i\u1ec3m $A$ sao cho $OA=2$ <br\/> Tr\u00ean tia $Oy$ l\u1ea5y \u0111i\u1ec3m $B$ sao cho $OB= 5$ <br\/> G\u00f3c $ABO$ l\u00e0 g\u00f3c c\u1ea7n d\u1ef1ng.<br\/>Th\u1eadt v\u1eady, ta c\u00f3 $tg\\,\\alpha=tg\\,\\widehat {ABO}=\\dfrac {OA}{OB}=\\dfrac {2}{5}$<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D6c.png' \/><\/center><br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B<\/span><\/span>","column":3}]}],"id_ques":1385},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["IM","MI"],["KM","MK"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","type_check":"","ques":"<span class='basic_left'>Cho h\u00ecnh v\u1ebd<\/span><br\/><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D5.png' \/>$\\,\\,$<br\/>$\\sin K=\\dfrac{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}$ ","hint":"T\u1ec9 s\u1ed1 gi\u1eefa c\u1ea1nh \u0111\u1ed1i v\u00e0 c\u1ea1nh huy\u1ec1n \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 sin c\u1ee7a g\u00f3c $\\alpha$","explain":"X\u00e9t $\\Delta IKM$ c\u00f3: $\\widehat{I}=90^o$ <br\/> $\\Rightarrow \\sin K=\\dfrac{IM}{KM}$<br\/><span class='basic_pink'>V\u1eady k\u1ebft qu\u1ea3 c\u1ea7n \u0111i\u1ec1n l\u00e0 $IM$ v\u00e0 $KM$<\/span>"}]}],"id_ques":1386},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["1082,5"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","type_check":"","ques":"<span class='basic_left'>Cho h\u00ecnh ch\u1eef nh\u1eadt $ABCD$, c\u00f3 \u0111\u01b0\u1eddng ch\u00e9o $AC= 50 cm$, $AC$ t\u1ea1o v\u1edbi $AB$ g\u00f3c $30^o$<br\/>(Bi\u1ebft $\\sin 30^o=0,5; \\,\\cos 30^o=0,866;$ $\\,tg\\, 30^o=0,577;\\,cotg\\,30^o=1,732$)<br\/>Di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt l\u00e0_input_ $(cm^2)$<\/span> ","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D4.png' \/><\/center><br\/>X\u00e9t $\\Delta ABC$ c\u00f3: $ \\widehat{B}=90^o$. <br\/>\u00c1p d\u1ee5ng h\u1ec7 th\u1ee9c v\u1ec1 c\u1ea1nh v\u00e0 g\u00f3c trong tam gi\u00e1c vu\u00f4ng, ta c\u00f3: <br\/>$AB=AC.cos 30^o$$=50.0,866=43,3\\, (cm)$<br\/>$BC=AC.sin 30^o=$$50.0,5=25 \\,(cm)$<br\/>$S_{ABCD}=AB.BC$$=43,3.25=1082,5\\,(cm^2)$<br\/><span class='basic_pink'>V\u1eady k\u1ebft qu\u1ea3 c\u1ea7n \u0111i\u1ec1n l\u00e0 $1082,5$<\/span><\/span><\/span>"}]}],"id_ques":1387},{"time":24,"part":[{"title":"Ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"select":["A. $4\\sqrt{3}$","B. $3\\sqrt{3}$","C. $2\\sqrt{3}$"],"ques":"<span class='basic_left'>Tam gi\u00e1c $ABC$ vu\u00f4ng t\u1ea1i $A$ c\u00f3 $AB= 12 cm$; $\\widehat {C}=30^o$; $BD$ l\u00e0 ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $ ABC$ ($D \\in AC$). <br\/>\u0110\u1ed9 d\u00e0i c\u1ea1nh $AD$ = ?$(cm)$<\/span>","hint":"T\u00ednh s\u1ed1 \u0111o $\\widehat{ABD}$","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D3.png' \/><\/center><br\/>X\u00e9t $\\Delta ABC$ c\u00f3: $ \\widehat{A}=90^o$<br\/>$ \\Rightarrow \\widehat{B}=90^o-\\widehat{C}=60^o\\\\ \\Rightarrow \\widehat{ABD}=\\dfrac{\\widehat{B}}{2}=30^o $($\\widehat B$ v\u00e0 $\\widehat C$ l\u00e0 hai g\u00f3c ph\u1ee5 nhau)<br\/>X\u00e9t $ \\Delta ADB$ c\u00f3: $\\widehat{A}=90^o$<br\/>$AD=AB.tg\\,\\widehat{ABD}$$=12.tg\\, 30^o=12.\\dfrac{\\sqrt{3}}{3}$$=4\\sqrt{3} \\,(cm)$<\/span>"}]}],"id_ques":1388},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["128,7"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","type_check":"","ques":"<span class='basic_left'>Tr\u00ean b\u1edd b\u00ean kia c\u1ee7a d\u00f2ng s\u00f4ng l\u1ea5y \u0111i\u1ec3m $B$, b\u1edd b\u00ean n\u00e0y ta l\u1ea5y \u0111i\u1ec3m $A$ \u0111\u1ed1i di\u1ec7n v\u1edbi $B$. \u0110\u1ec3 \u0111o gi\u00e1n ti\u1ebfp \u0111\u1ed9 r\u1ed9ng c\u1ee7a d\u00f2ng s\u00f4ng (kho\u1ea3ng c\u00e1ch $AB$), ng\u01b0\u1eddi ta l\u1ea5y \u0111i\u1ec3m $C$ b\u00ean n\u00e0y s\u00f4ng v\u00e0 c\u00e1ch $A$ m\u1ed9t kho\u1ea3ng $AC=90$ m\u00e9t, \u0111\u1eb7t gi\u00e1c k\u1ebf t\u1ea1i $C$ \u0111o \u0111\u01b0\u1ee3c g\u00f3c $\\widehat{ACB}=55^o$. <br\/>Chi\u1ec1u r\u1ed9ng $AB$ c\u1ee7a con s\u00f4ng l\u00e0:_input_$(m)$<br\/>(Cho bi\u1ebft $\\sin 55^o=0,82;\\,\\cos55^o=0,57;$ $\\, tg\\,55^o=1,43; \\,cotg\\,55^o=0,7$)<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D2.png' \/><\/center><\/span> ","explain":"<span class='basic_left'>X\u00e9t $\\Delta ABC $ c\u00f3: $\\widehat{A}=90^o$.<br\/> \u00c1p d\u1ee5ng h\u1ec7 th\u1ee9c v\u1ec1 c\u1ea1nh v\u00e0 g\u00f3c trong tam gi\u00e1c vu\u00f4ng, ta c\u00f3: <br\/>$AB=AC.tg\\, C$$=90.tg\\,55^o=128,7 \\,(m)$<br\/><span class='basic_pink'>V\u1eady k\u1ebft qu\u1ea3 c\u1ea7n \u0111i\u1ec1n l\u00e0 $128,7$<\/span><\/span><\/span>"}]}],"id_ques":1389},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"\u0110\u1ecbnh ngh\u0129a c\u00e1c t\u1ec9 s\u1ed1 l\u01b0\u1ee3ng gi\u00e1c c\u1ee7a g\u00f3c nh\u1ecdn l\u00e0:<br\/>(Vi\u1ebft t\u1eaft: c\u1ea1nh k\u1ec1 (k); c\u1ea1nh \u0111\u1ed1i (\u0111); c\u1ea1nh huy\u1ec1n (h)) ","select":["A. $sin\\,=\\dfrac{\u0111}{h};\\,cos=\\dfrac{k}{h};$ $tg\\,=\\dfrac{\u0111}{k};\\,cotg=\\dfrac{k}{\u0111}$ ","B. $sin\\,=\\dfrac{k}{h};\\,cos=\\dfrac{\u0111}{h};$ $tg\\,=\\dfrac{\u0111}{k};\\,cotg=\\dfrac{k}{\u0111}$","C. $sin\\,=\\dfrac{\u0111}{h};\\,cos=\\dfrac{k}{h};$ $tg\\,=\\dfrac{k}{\u0111};\\,cotg=\\dfrac{\u0111}{k}$"],"explain":" <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai4/lv1/img\/H914_D1.png' \/><\/center><br\/>$sin\\,\\alpha=\\dfrac{\u0111}{h}$;$\\,\\,\\,\\,\\,$$cos\\,\\alpha=\\dfrac{k}{h}$<br\/>$tg\\,\\alpha=\\dfrac{\u0111}{k}$;$\\,\\,\\,\\,\\,\\,$$cotg\\,\\alpha=\\dfrac{k}{\u0111}$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A<\/span>","column":1}]}],"id_ques":1390}],"lesson":{"save":0,"level":1}}