{"segment":[{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["135"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"<span class='basic_left'> M\u1ed7i g\u00f3c trong c\u1ee7a b\u00e1t gi\u00e1c \u0111\u1ec1u c\u00f3 s\u1ed1 \u0111o l\u00e0 $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ <\/span> ","explain":" <span class='basic_left'> T\u1ed5ng c\u00e1c g\u00f3c trong c\u1ee7a b\u00e1t gi\u00e1c \u0111\u1ec1u l\u00e0: <br\/> $(8-2).180^o=1080^o$ <br\/> S\u1ed1 \u0111o m\u1ed7i g\u00f3c trong c\u1ee7a b\u00e1t gi\u00e1c \u0111\u1ec1u l\u00e0: <br\/> $1080^o:8=135^o$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $135$. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> S\u1ed1 \u0111o m\u1ed7i g\u00f3c trong c\u1ee7a \u0111a gi\u00e1c \u0111\u1ec1u n c\u1ea1nh l\u00e0: $\\dfrac{(n-2)180^o}{n}$ ($n > 2$) <\/i> <\/span> "}]}],"id_ques":1581},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["54"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho \u0111a gi\u00e1c c\u00f3 $12$ c\u1ea1nh, s\u1ed1 \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a \u0111a gi\u00e1c $12$ c\u1ea1nh \u0111\u00f3 l\u00e0 $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$ <\/span> ","explain":" <span class='basic_left'> S\u1ed1 \u0111\u01b0\u1eddng ch\u00e9o c\u1ee7a \u0111a gi\u00e1c $12$ c\u1ea1nh \u0111\u00f3 l\u00e0: <br\/> $\\dfrac{12(12-3)}{2}$$=\\dfrac{108}{2}=54$ (\u0111\u01b0\u1eddng). <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $54$. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> S\u1ed1 \u0111\u01b0\u1eddng ch\u00e9o trong \u0111a gi\u00e1c $n$ c\u1ea1nh l\u00e0: $\\dfrac{n(n-3)}{2}$ $(n>3)$<\/i> <\/span> "}]}],"id_ques":1582},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["8"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"<span class='basic_left'> N\u1ebfu \u0111a gi\u00e1c c\u00f3 s\u1ed1 \u0111\u01b0\u1eddng ch\u00e9o l\u00e0 $20$ th\u00ec \u0111a gi\u00e1c c\u00f3 bao nhi\u00eau c\u1ea1nh? <br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$ c\u1ea1nh <\/span> ","explain":" <span class='basic_left'> G\u1ecdi s\u1ed1 c\u1ea1nh c\u1ee7a \u0111a gi\u00e1c theo b\u00e0i l\u00e0 $n$. <br\/> Ta c\u00f3: <br\/> $\\dfrac{n(n-3)}{2}=20$ <br\/> $\\Leftrightarrow n(n-3)=40$ <br\/> $\\Leftrightarrow n^2-3n-40=0$ <br\/> $\\Leftrightarrow n^2-8n+5n-40=0$ <br\/> $\\Leftrightarrow n(n-8)+5(n-8)=0$ <br\/> $\\Leftrightarrow (n-8)(n+5)=0$ <br\/> Do $n\\ge 0$ n\u00ean $n+5\\ne 0$ n\u00ean $(n-8)(n+5)=0\\Rightarrow n-8=0 \\Rightarrow n=8$. <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $8$. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> S\u1ed1 \u0111\u01b0\u1eddng ch\u00e9o trong \u0111a gi\u00e1c \u0111\u1ec1u $n$ c\u1ea1nh l\u00e0: $\\dfrac{n(n-3)}{2}$ <\/i> <\/span> "}]}],"id_ques":1583},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["4"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"<span class='basic_left'> T\u1ed5ng s\u1ed1 \u0111o c\u00e1c g\u00f3c ngo\u00e0i c\u1ee7a \u0111a gi\u00e1c l\u1ed3i $n$ c\u1ea1nh b\u1eb1ng t\u1ed5ng s\u1ed1 \u0111o c\u00e1c g\u00f3c trong c\u1ee7a \u0111a gi\u00e1c \u0111\u00f3. <br\/> \u0110a gi\u00e1c \u0111\u00f3 c\u00f3 bao nhi\u00eau c\u1ea1nh? <br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $n=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$ (c\u1ea1nh) <\/span> ","explain":" <span class='basic_left'> T\u1ed5ng s\u1ed1 \u0111o c\u00e1c g\u00f3c trong c\u1ee7a \u0111a gi\u00e1c $n$ c\u1ea1nh l\u00e0: $(n-2).180^o$ <br\/> T\u1ed5ng s\u1ed1 \u0111o c\u00e1c g\u00f3c ngo\u00e0i c\u1ee7a \u0111a gi\u00e1c $n$ c\u1ea1nh l\u00e0: $n.180^o-(n-2).180^o=360^o$ <br\/> M\u00e0 theo gi\u1ea3 thi\u1ebft th\u00ec: T\u1ed5ng c\u00e1c g\u00f3c ngo\u00e0i c\u1ee7a \u0111a gi\u00e1c l\u1ed3i $n$ c\u1ea1nh b\u1eb1ng t\u1ed5ng c\u00e1c g\u00f3c trong c\u1ee7a \u0111a gi\u00e1c \u0111\u00f3 n\u00ean: <br\/> $(n-2).180^o=360^o$ <br\/> $\\Leftrightarrow n.180^0-360^o=360^o$ <br\/> $\\Leftrightarrow n.180^o=720^o$ <br\/> $\\Leftrightarrow n=720^o:180^o=4$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $4$. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> T\u1ed5ng s\u1ed1 \u0111o c\u00e1c g\u00f3c ngo\u00e0i c\u1ee7a \u0111a gi\u00e1c $n$ c\u1ea1nh l\u00e0: $360^o$ <\/i> <\/span> "}]}],"id_ques":1584},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":" <span class='basic_left'> M\u1ed9t h\u00ecnh ch\u1eef nh\u1eadt n\u1ebfu gi\u1ea3m \u0111\u1ed3ng th\u1eddi chi\u1ec1u d\u00e0i v\u00e0 chi\u1ec1u r\u1ed9ng \u0111i $20$% th\u00ec di\u1ec7n t\u00edch c\u1ee7a n\u00f3 gi\u1ea3m \u0111i $9\\,m^2$. Di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt l\u00fac \u0111\u1ea7u l\u00e0: <\/span>","select":[" A. $18\\,m^2$"," B. $25\\,m^2$","C. $35\\,m^2$","D. $12\\,m^2$"],"explain":" <span class='basic_left'> G\u1ecdi chi\u1ec1u d\u00e0i v\u00e0 chi\u1ec1u r\u1ed9ng c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt ban \u0111\u1ea7u l\u00e0 $a$ v\u00e0 $b$ $(a > b)$ $(\\,m)$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt ban \u0111\u1ea7u l\u00e0: $S_{\\text{\u0111}}=ab\\,\\, (m^2)$ <br\/> Gi\u1ea3m chi\u1ec1u d\u00e0i \u0111i $20$% th\u00ec chi\u1ec1u d\u00e0i m\u1edbi l\u00e0: $\\dfrac{80a}{100}=\\dfrac{4a}{5}$ $(m)$ <br\/> Gi\u1ea3m chi\u1ec1u r\u1ed9ng \u0111i $20$% th\u00ec chi\u1ec1u r\u1ed9ng m\u1edbi l\u00e0: $\\dfrac{80b}{100}=\\dfrac{4b}{5}$ $(m)$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt l\u00fac sau l\u00e0: <br\/> $S_s=\\dfrac{4a}{5} \\cdot \\dfrac{4b}{5}$$=\\dfrac{16ab}{25}\\,\\,(m^2)$ <br\/> Theo b\u00e0i, ta c\u00f3: <br\/> $ S_{\\text{\u0111}}-S_s=9$ <br\/> $\\Rightarrow ab-\\dfrac{16ab}{25}=9$ <br\/> $\\Rightarrow \\dfrac{9ab}{25}=9$ <br\/> $\\Rightarrow ab=25\\,\\,(m^2)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B. <\/span> <\/span> ","column":4}]}],"id_ques":1585},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":10,"ques":" <span class='basic_left'> Cho $\\Delta ABC$ c\u00f3 $AB=2AC$. T\u1ec9 s\u1ed1 \u0111\u01b0\u1eddng cao xu\u1ea5t ph\u00e1t t\u1eeb $B$ v\u00e0 $C$ l\u00e0: <\/span>","select":[" A. $\\dfrac{1}{2}$"," B. $\\dfrac{1}{3}$","C. $3$","D. $2$"],"hint":" T\u00ednh di\u1ec7n t\u00edch $\\Delta ABC$ theo \u0111\u01b0\u1eddng cao xu\u1ea5t ph\u00e1t t\u1eeb $B$ v\u00e0 xu\u1ea5t ph\u00e1t t\u1eeb $C$. <br\/> T\u1eeb \u0111\u00f3 suy ra t\u1ec9 s\u1ed1 c\u1ea7n t\u00ecm.","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai11/lv3/img\/H821_K1_1.png' \/><\/center> G\u1ecdi \u0111\u01b0\u1eddng cao xu\u1ea5t ph\u00e1t t\u1eeb \u0111\u1ec9nh $B$ l\u00e0 $h$, xu\u1ea5t ph\u00e1t t\u1eeb \u0111\u1ec9nh $C$ l\u00e0 $h'$. <br\/> Di\u1ec7n t\u00edch $\\Delta ABC$ t\u00ednh theo $h$ l\u00e0: <br\/> $S_{ABC}=\\dfrac{1}{2}.h.AC$ <br\/> Di\u1ec7n t\u00edch $\\Delta ABC$ t\u00ednh theo $h'$ l\u00e0: <br\/> $S_{ABC}=\\dfrac{1}{2}.h'.AB$ <br\/> Do \u0111\u00f3: <br\/> $\\dfrac{1}{2}.h.AC=\\dfrac{1}{2}.h'.AB$ <br\/> $\\Rightarrow \\dfrac{h}{h'}=\\dfrac{AB}{AC}=2$ <br\/> T\u1ec9 s\u1ed1 \u0111\u01b0\u1eddng cao xu\u1ea5t ph\u00e1t t\u1eeb \u0111\u1ec9nh $B$ v\u00e0 $C$ l\u00e0 $2$. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 D. <\/span> <\/span> ","column":2}]}],"id_ques":1586},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":" <span class='basic_left'> Cho $\\Delta ABC$ c\u00f3 $AM$ l\u00e0 trung tuy\u1ebfn, $S_{AMB}=22,5\\,cm^2$ <br\/> Di\u1ec7n t\u00edch $\\Delta ABC$ l\u00e0: <\/span>","select":[" A. $135\\,cm^2$"," B. $45\\,cm^2$","C. $67,5\\,cm^2$","D. $50\\,cm^2$"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai11/lv3/img\/H821_K1_2.jpg' \/><\/center> $\\Delta ABC$ c\u00f3 $AM$ l\u00e0 trung tuy\u1ebfn n\u00ean: $BC=2BM$ <br\/> G\u1ecdi $AH$ l\u00e0 \u0111\u01b0\u1eddng cao t\u1eeb \u0111\u1ec9nh $A$ <br\/> $S_{ABC}=\\dfrac{1}{2}AH.BC$$=2.\\dfrac{1}{2}AH.BM=2S_{AMB}$ <br\/> $\\Rightarrow S_{ABC}=2.22,5=45\\,(cm^2)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B. <\/span> <\/span> ","column":4}]}],"id_ques":1587},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai11/lv3/img\/H821_K1_3.jpg' \/><\/center> Cho $\\Delta ABC$ c\u00f3 $G$ l\u00e0 tr\u1ecdng t\u00e2m nh\u01b0 tr\u00ean h\u00ecnh v\u1ebd. \u0110i\u1ec3m $K$ thu\u1ed9c $AB$ sao cho: $AK=BK$ <br\/> T\u1ec9 s\u1ed1 di\u1ec7n t\u00edch gi\u1eefa $\\Delta KGB$ v\u00e0 $\\Delta GBC$ l\u00e0: <\/span>","select":[" A. $2$"," B. $3$","C. $\\dfrac{1}{2}$","D. $\\dfrac{1}{3}$"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai11/lv3/img\/H821_K1_3.jpg' \/><\/center> Hai tam gi\u00e1c $KGB$ v\u00e0 $GBC$ c\u00f3 c\u00f9ng \u0111\u01b0\u1eddng cao t\u1eeb \u0111\u1ec9nh $B$ xu\u1ed1ng hai c\u1ea1nh \u0111\u00e1y $KG$ v\u00e0 $GC$ <br\/> M\u00e0 theo t\u00ednh ch\u1ea5t c\u1ee7a tr\u1ecdng t\u00e2m $G$ th\u00ec: $GC=2KG$ <br\/> $\\Rightarrow S_{\\Delta GBC}=2S_{\\Delta KGB}$ <br\/> $\\Rightarrow \\dfrac{S_{\\Delta KGB}}{S_{\\Delta GBC}}=\\dfrac{1}{2}$ <br\/> T\u1ec9 s\u1ed1 di\u1ec7n t\u00edch gi\u1eefa $\\Delta KGB$ v\u00e0 $\\Delta GBC$ l\u00e0 $\\dfrac{1}{2}$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span> <\/span> ","column":2}]}],"id_ques":1588},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":" <span class='basic_left'> Cho h\u00ecnh v\u1ebd sau <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai11/lv3/img\/H821_K1_4.jpg' \/><\/center> Bi\u1ebft $\\Delta ABC$ \u0111\u1ec1u c\u1ea1nh $a$. <br\/> Di\u1ec7n t\u00edch $\\Delta DEF$ \u0111\u01b0\u1ee3c t\u00f4 m\u00e0u trong h\u00ecnh v\u1ebd tr\u00ean l\u00e0: <\/span>","select":[" A. $\\dfrac{a^2\\sqrt{3}}{8}$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch)"," B. $\\dfrac{a^2\\sqrt{3}}{12}$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch)","C. $\\dfrac{a^2\\sqrt{3}}{16}$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch)","D. $\\dfrac{a^2\\sqrt{3}}{4}$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch)"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai11/lv3/img\/H821_K1_4.jpg' \/><\/center> Theo h\u00ecnh v\u1ebd \u0111\u00e3 cho: $AD=AE=EC=CF=BF=BD$ <br\/> Ta l\u1ea1i c\u00f3 $DE=DF=EF=\\dfrac{AB}{2}=AD$<br\/>M\u00e0 $\\Delta ABC$ \u0111\u1ec1u c\u1ea1nh $a$. <br\/> $\\Rightarrow \\Delta ADE =\\Delta CEF=\\Delta BDF=\\Delta DEF$ <br\/> Do \u0111\u00f3: $S_{\\Delta DEF}=\\dfrac{1}{4}S_{\\Delta ABC}$ <br\/> Ta c\u00f3 tam gi\u00e1c $ABC$ \u0111\u1ec1u, $FB=FC$ (gi\u1ea3 thi\u1ebft)<br\/> $\\Rightarrow AF \\bot BC$. <br\/> $\\Rightarrow AF^2+BF^2=AB^2$ (\u0111\u1ecbnh l\u00ed Pi - ta - go) <br\/> $\\Rightarrow AF^2=AB^2-BF^2$ <br\/> $\\Rightarrow AF^2=a^2-\\dfrac{a^2}{4}$ <br\/> $\\Rightarrow AF=\\dfrac{a\\sqrt{3}}{2}$ <br\/> Di\u1ec7n t\u00edch $\\Delta ABC$ l\u00e0: <br\/> $S_{\\Delta ABC}=\\dfrac{1}{2}.AF.BC$ <br\/> $=\\dfrac{1}{2}.\\dfrac{a\\sqrt{3}}{2}.a $<br\/> $=\\dfrac{a^2\\sqrt{3}}{4}$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch) <br\/> $\\Rightarrow S_{\\Delta DEF}=\\dfrac{1}{4}S_{\\Delta ABC}$ <br\/> $=\\dfrac{1}{4}.\\dfrac{a^2\\sqrt{3}}{4}$ <br\/> $=\\dfrac{a^2\\sqrt{3}}{16}$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch) <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C. <\/span> <br\/><b>L\u01b0u \u00fd:<\/b><i> Hai tam gi\u00e1c b\u1eb1ng nhau th\u00ec di\u1ec7n t\u00edch c\u1ee7a ch\u00fang b\u1eb1ng nhau. <\/i> <\/span>","column":2}]}],"id_ques":1589},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai11/lv3/img\/H821_K1_5.jpg' \/><\/center> Cho h\u00ecnh ch\u1eef nh\u1eadt $ABCD$ nh\u01b0 h\u00ecnh v\u1ebd. Bi\u1ebft $\\widehat{ABD}=30^o; BD=8 \\,cm$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt $ABCD$ l\u00e0: <\/span>","select":[" A. $16\\sqrt{3}\\,cm^2$ "," B. $16\\,cm^2$ ","C. $32\\,cm^2$","D. $16\\sqrt{2}\\,cm^2$ "],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai11/lv3/img\/H821_K1_5.jpg' \/><\/center> X\u00e9t tam gi\u00e1c vu\u00f4ng $ABD$ c\u00f3: $\\widehat{ABD}=30^o$ <br\/> $\\Rightarrow BD=2AD$ <br\/> $\\Rightarrow AD=4\\,cm$ <br\/> \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Py - ta - go v\u00e0o tam gi\u00e1c vu\u00f4ng $ABD$ ta c\u00f3: <br\/> $AB^2+AD^2=BD^2$ <br\/> $\\Rightarrow AB^2=BD^2-AD^2$ <br\/> $\\Rightarrow AB^2=8^2-4^2=48$ <br\/> $\\Rightarrow AB=4\\sqrt{3}\\,(cm)$ <br\/> Di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt $ABCD$ l\u00e0: <br\/> $AB.AD=4\\sqrt{3}.4=16\\sqrt{3}\\,(cm^2)$ <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> Trong tam gi\u00e1c vu\u00f4ng c\u00f3 m\u1ed9t g\u00f3c nh\u1ecdn b\u1eb1ng $30^o$ th\u00ec \u0111\u1ed9 d\u00e0i c\u1ea1nh huy\u1ec1n g\u1ea5p \u0111\u00f4i c\u1ea1nh g\u00f3c vu\u00f4ng \u0111\u1ed1i di\u1ec7n v\u1edbi g\u00f3c $30^o$. <\/i> <\/span> ","column":2}]}],"id_ques":1590}],"lesson":{"save":0,"level":3}}