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{"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":10,"ques":" <span class='basic_left'> C\u00e1c h\u00ecnh c\u00f3 tr\u1ee5c \u0111\u1ed1i x\u1ee9ng l\u00e0: <\/span>","select":["A. H\u00ecnh b\u00ecnh h\u00e0nh, h\u00ecnh ch\u1eef nh\u1eadt, h\u00ecnh vu\u00f4ng","B. H\u00ecnh thang c\u00e2n, tam gi\u00e1c c\u00e2n, h\u00ecnh thoi","C. Tam gi\u00e1c c\u00e2n, h\u00ecnh b\u00ecnh h\u00e0nh, h\u00ecnh vu\u00f4ng","D. H\u00ecnh thang, tam gi\u00e1c \u0111\u1ec1u, h\u00ecnh vu\u00f4ng"],"explain":" <span class='basic_left'> C\u00e1c h\u00ecnh c\u00f3 \u0111\u1ed1i x\u1ee9ng tr\u1ee5c l\u00e0 h\u00ecnh thang c\u00e2n, tam gi\u00e1c c\u00e2n, h\u00ecnh thoi. <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_D1_8.jpg' \/><\/center> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_D2_3.jpg' \/><\/center> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_D2_11.jpg' \/><\/center> <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B. <\/span><\/span> ","column":1}]}],"id_ques":1421},{"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 c\u00e1c h\u00ecnh v\u1ebd sau <br\/> <img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_K1_1.jpg' \/> <img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_K1_1b.jpg' \/> <img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_K1_1c.jpg' \/> <br\/> H\u00ecnh n\u00e0o kh\u00f4ng c\u00f3 t\u00e2m \u0111\u1ed1i x\u1ee9ng? <\/span>","select":["A. H\u00ecnh 1","B. H\u00ecnh 2","C. H\u00ecnh 3","D. H\u00ecnh 2 v\u00e0 h\u00ecnh 3"],"explain":" <span class='basic_left'> H\u00ecnh 1: H\u00ecnh b\u00ecnh h\u00e0nh c\u00f3 t\u00e2m \u0111\u1ed1i x\u1ee9ng l\u00e0 giao c\u1ee7a hai \u0111\u01b0\u1eddng ch\u00e9o. <br\/> H\u00ecnh 3: C\u00f3 t\u00e2m \u0111\u1ed1i x\u1ee9ng l\u00e0 t\u00e2m c\u1ee7a \u0111\u01b0\u1eddng tr\u00f2n. <br\/> H\u00ecnh 2 kh\u00f4ng c\u00f3 t\u00e2m \u0111\u1ed1i x\u1ee9ng. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B. <\/span><\/span> ","column":2}]}],"id_ques":1422},{"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'> H\u00ecnh b\u00ecnh h\u00e0nh $ABCD$ c\u00f3 n\u1eeda chu vi l\u00e0 $19\\, cm$, c\u1ea1nh $AB=11\\,cm$. Khi \u0111\u00f3 h\u00ecnh b\u00ecnh h\u00e0nh $A'B'C'D'$ \u0111\u1ed1i x\u1ee9ng v\u1edbi $ABCD$ qua \u0111\u01b0\u1eddng th\u1eb3ng $d$. N\u1eeda chu vi c\u1ee7a h\u00ecnh b\u00ecnh h\u00e0nh $A'B'C'D'$ v\u00e0 \u0111\u1ed9 d\u00e0i c\u1ea1nh $A'D'$ l\u1ea7n l\u01b0\u1ee3t l\u00e0: <\/span>","select":["A. $11\\,\\, cm$ v\u00e0 $8 \\,\\, cm$","B. $11 \\,\\,cm$ v\u00e0 $19 \\,\\, cm$","C. $19 \\,\\, cm$ v\u00e0 $11 \\,\\, cm$","D. $19 \\,\\, cm$ v\u00e0 $8 \\,\\, cm$"],"explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>Hai h\u00ecnh \u0111\u1ed1i x\u1ee9ng nhau qua tr\u1ee5c \u0111\u1ed1i x\u1ee9ng th\u00ec c\u00f3 chu vi b\u1eb1ng nhau. <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Theo b\u00e0i, $A'B'C'D'$ \u0111\u1ed1i x\u1ee9ng v\u1edbi $ABCD$ qua tr\u1ee5c $d$ n\u00ean chu vi c\u1ee7a $A'B'C'D'$ b\u1eb1ng v\u1edbi chu vi c\u1ee7a $ABCD$. <br\/> Do \u0111\u00f3: n\u1eeda chu vi c\u1ee7a $A'B'C'D'$ l\u00e0 $19\\, cm$. <br\/> M\u00e0 n\u1eeda chu vi c\u1ee7a $ABCD$ l\u00e0: $AB+AD=19 \\, (cm) $<br\/> $\\Rightarrow AD=19-11=8\\,(cm)$ <br\/> Do \u0111\u00f3 $A'D'=AD=8\\, (cm)$ ($AD, A'D'$ \u0111\u1ed1i x\u1ee9ng v\u1edbi nhau qua $d$). <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 D. <\/span><\/span> ","column":2}]}],"id_ques":1423},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"fill_the_blank","correct":[[["OH"]]],"list":[{"point":10,"width":20,"type_input":"","ques":"<span class='basic_left'> Cho g\u00f3c $xOy$ v\u00e0 \u0111i\u1ec3m $M$ n\u1eb1m trong g\u00f3c \u0111\u00f3. G\u1ecdi $M_1; M_2$ theo th\u1ee9 t\u1ef1 l\u00e0 \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng c\u1ee7a $M$ qua $Ox$ v\u00e0 $Oy$. G\u1ecdi $Oz$ l\u00e0 tia ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $xOy, H$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $M_1M_2$. <br\/><br\/> <b> C\u00e2u 1:<\/b> $M_1$ v\u00e0 $M_2$ \u0111\u1ed1i x\u1ee9ng v\u1edbi nhau qua \u0111\u01b0\u1eddng th\u1eb3ng $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$ <\/span> ","explain":" <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_K1_2.jpg' \/><\/center> <span class='basic_left'> \u0110\u01b0\u1eddng th\u1eb3ng ch\u1ee9a tia $Ox$ l\u00e0 \u0111\u01b0\u1eddng trung tr\u1ef1c c\u1ee7a $MM_1$. <br\/> $\\Rightarrow OM_1=OM$ <br\/> T\u01b0\u01a1ng t\u1ef1: $OM_2=OM$ <br\/> $\\Rightarrow OM_1=OM_2$ <br\/> $\\Delta OM_1M_2$ c\u00e2n t\u1ea1i \u0111\u1ec9nh $O$ n\u00ean trung tuy\u1ebfn $OH$ \u0111\u1ed3ng th\u1eddi l\u00e0 \u0111\u01b0\u1eddng trung tr\u1ef1c c\u1ee7a $M_1M_2$. <br\/> Suy ra $M_1$ v\u00e0 $M_2$ \u0111\u1ed1i x\u1ee9ng v\u1edbi nhau qua \u0111\u01b0\u1eddng th\u1eb3ng $OH$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $OH$. <\/span><\/span> "}]}],"id_ques":1424},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"fill_the_blank","correct":[[["100"]]],"list":[{"point":10,"width":20,"type_input":"","ques":"<span class='basic_left'> Cho g\u00f3c $xOy$ v\u00e0 \u0111i\u1ec3m $M$ n\u1eb1m trong g\u00f3c \u0111\u00f3. G\u1ecdi $M_1; M_2$ theo th\u1ee9 t\u1ef1 l\u00e0 \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng c\u1ee7a $M$ qua $Ox$ v\u00e0 $Oy$. G\u1ecdi $Oz$ l\u00e0 tia ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $xOy, H$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $M_1M_2$. <br\/><br\/> <b> C\u00e2u 2:<\/b> Cho $\\widehat{xOy}=50^o$. T\u00ednh $\\widehat{M_1OM_2}$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $\\widehat{M_1OM_2}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ <\/span> ","explain":" <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_K1_2.jpg' \/><\/center> <span class='basic_left'> Gi\u1ea3 s\u1eed $\\widehat{MOx}=a^o; \\widehat{MOy}=50^o-a^o$ <br\/> Theo t\u00ednh ch\u1ea5t c\u1ee7a tr\u1ee5c \u0111\u1ed1i x\u1ee9ng: <br\/> $\\widehat{M_1Ox}=\\widehat{MOx}=a^o$ $\\Rightarrow \\widehat{M_1OM}=\\widehat{M_1Ox}+\\widehat{MOx}=2a^o$ <br\/> T\u01b0\u01a1ng t\u1ef1: $\\widehat{MOy}=\\widehat{M_2Oy}=50^o-a^o$ <br\/> $\\Rightarrow \\widehat{MOM_2}=2(50^o-a^o)$ <br\/> $\\Rightarrow \\widehat{M_1OM_2}=\\widehat{M_1OM}+\\widehat{MOM_2}$$=2a^o+2(50^o-a^o)=100^o$. <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $100$. <\/span><\/span> "}]}],"id_ques":1425},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho ba c\u00e2u","temp":"fill_the_blank","correct":[[["Oz"]]],"list":[{"point":10,"width":20,"type_input":"","ques":"<span class='basic_left'> Cho g\u00f3c $xOy$ v\u00e0 \u0111i\u1ec3m $M$ n\u1eb1m trong g\u00f3c \u0111\u00f3. G\u1ecdi $M_1; M_2$ theo th\u1ee9 t\u1ef1 l\u00e0 \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng c\u1ee7a $M$ qua $Ox$ v\u00e0 $Oy$. G\u1ecdi $Oz$ l\u00e0 tia ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $xOy, H$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $M_1M_2$. <br\/><br\/> <b> C\u00e2u 3:<\/b> Tr\u1ee5c \u0111\u1ed1i x\u1ee9ng c\u1ee7a g\u00f3c $MOH$ l\u00e0 _input_ <\/span> ","explain":" V\u1ebd h\u00ecnh <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_K1_2.jpg' \/><\/center> <span class='basic_left'> Gi\u1ea3 s\u1eed $M$ n\u1eb1m trong g\u00f3c $xOz$, ta c\u00f3: <br\/> $\\begin{align}& \\widehat{MOz}=\\widehat{xOz}-\\widehat{xOM}={{25}^{o}}-{{a}^{o}} \\\\ & \\widehat{HOz}=\\widehat{{{M}_{1}}OH}-\\widehat{{{M}_{1}}Oz} \\\\ & =\\dfrac{1}{2}\\widehat{{{M}_{1}}O{{M}_{2}}}-\\left( \\widehat{{{M}_{1}}OM}+\\widehat{MOz} \\right) \\\\ & ={{50}^{o}}-\\left( 2{{a}^{o}}+{{25}^{o}}-{{a}^{o}} \\right) \\\\ & ={{25}^{o}}-{{a}^{o}} \\\\ & \\Rightarrow \\widehat{MOz}=\\widehat{HOz} \\\\ \\end{align}$ <br\/> Do \u0111\u00f3 $Oz$ l\u00e0 ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $MOH$ hay $Oz$ l\u00e0 tr\u1ee5c \u0111\u1ed1i x\u1ee9ng c\u1ee7a g\u00f3c $MOH$. <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $Oz$. <br\/> <span class='basic_green'> <b> L\u01b0u \u00fd:<\/b> <\/span> <i> Tr\u1ee5c \u0111\u1ed1i x\u1ee9ng c\u1ee7a m\u1ed9t g\u00f3c ch\u00ednh l\u00e0 \u0111\u01b0\u1eddng ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c \u0111\u00f3. <\/i> <\/span> <\/span>"}]}],"id_ques":1426},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho b\u1ed1n c\u00e2u","temp":"fill_the_blank","correct":[[["="]]],"list":[{"point":10,"width":20,"type_input":"","ques":"<span class='basic_left'> Cho $\\Delta ABC$, $O$ l\u00e0 giao \u0111i\u1ec3m c\u1ee7a c\u00e1c \u0111\u01b0\u1eddng trung tr\u1ef1c c\u1ee7a ba c\u1ea1nh. G\u1ecdi $O_1; O_2; O_3$ theo th\u1ee9 t\u1ef1 l\u00e0 c\u00e1c \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng v\u1edbi \u0111i\u1ec3m $O$ qua c\u00e1c c\u1ea1nh $BC, CA$ v\u00e0 $AB$. <br\/><br\/> <b> C\u00e2u 1:<\/b> So s\u00e1nh \u0111\u1ed9 d\u00e0i $O_2O_3$ v\u1edbi $BC$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $O_2O_3\\, \\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\, BC$ <\/span> ","hint":"So s\u00e1nh qua \u0111\u01b0\u1eddng trung b\u00ecnh c\u1ee7a $\\Delta O_2OO_3$ v\u00e0 $\\Delta ABC$. ","explain":" <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_K1_3.jpg' \/><\/center> <span class='basic_left'> G\u1ecdi $D, E$ v\u00e0 $F$ theo th\u1ee9 t\u1ef1 l\u00e0 trung \u0111i\u1ec3m $BC; CA$ v\u00e0 $AB$. <br\/> D\u1ec5 th\u1ea5y $E$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $OO_2$; $F$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $OO_3$. <br\/> Trong $\\Delta O_2OO_3$ c\u00f3 $EF$ l\u00e0 \u0111\u01b0\u1eddng trung b\u00ecnh <br\/> $\\Rightarrow EF=\\dfrac{1}{2}O_2O_3$, $EF \/\/ O_2O_3$ (1) <br\/> Trong $\\Delta ABC$ c\u00f3 $EF$ l\u00e0 \u0111\u01b0\u1eddng trung b\u00ecnh <br\/> $\\Rightarrow EF=\\dfrac{1}{2}BC$, $EF \/\/ BC$ (2) <br\/> T\u1eeb (1) v\u00e0 (2) $\\Rightarrow O_2O_3=BC$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $=$. <\/span><\/span> "}]}],"id_ques":1427},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho b\u1ed1n c\u00e2u","temp":"fill_the_blank","correct":[[["ABC"]]],"list":[{"point":10,"width":20,"type_input":"","ques":"<span class='basic_left'> Cho $\\Delta ABC$, $O$ l\u00e0 giao \u0111i\u1ec3m c\u1ee7a c\u00e1c \u0111\u01b0\u1eddng trung tr\u1ef1c c\u1ee7a ba c\u1ea1nh. G\u1ecdi $O_1; O_2; O_3$ theo th\u1ee9 t\u1ef1 l\u00e0 c\u00e1c \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng v\u1edbi \u0111i\u1ec3m $O$ qua c\u00e1c c\u1ea1nh $BC, CA$ v\u00e0 $AB$. <br\/><br\/> <b> C\u00e2u 2:<\/b> $\\Delta O_1O_2O_3=\\Delta \\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{} $ (c - c - c) <\/span> ","explain":" V\u1ebd h\u00ecnh <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_K1_3.jpg' \/><\/center> <span class='basic_left'> Theo c\u00e2u 1, ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c: $O_2O_3=BC$ <br\/> T\u01b0\u01a1ng t\u1ef1, ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c: $O_1O_3=AC; O_1O_2=AB$ <br\/> X\u00e9t $\\Delta O_1O_2O_3 $ v\u00e0 $\\Delta ABC$ c\u00f3: <br\/> + $O_2O_3=BC$ <br\/> + $O_1O_3=AC$ <br\/> + $O_1O_2=AB$ <br\/> $\\Rightarrow \\Delta O_1O_2O_3=\\Delta ABC$ (c - c - c) <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $ABC$. <\/span><\/span> "}]}],"id_ques":1428},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho b\u1ed1n c\u00e2u","temp":"fill_the_blank","correct":[[["90"]]],"list":[{"point":10,"width":20,"type_input":"","ques":"<span class='basic_left'> Cho $\\Delta ABC$, $O$ l\u00e0 giao \u0111i\u1ec3m c\u1ee7a c\u00e1c \u0111\u01b0\u1eddng trung tr\u1ef1c c\u1ee7a ba c\u1ea1nh. G\u1ecdi $O_1; O_2; O_3$ theo th\u1ee9 t\u1ef1 l\u00e0 c\u00e1c \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng v\u1edbi \u0111i\u1ec3m $O$ qua c\u00e1c c\u1ea1nh $BC, CA$ v\u00e0 $AB$. <br\/><br\/> <b> C\u00e2u 3:<\/b> G\u00f3c t\u1ea1o b\u1edfi hai \u0111\u01b0\u1eddng th\u1eb3ng $O_1O$ v\u00e0 $O_2O_3$ l\u00e0 $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ <\/span> ","explain":" <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_K1_3.jpg' \/><\/center> <span class='basic_left'> Ta c\u00f3: $O_2O_3 \/\/EF$ v\u00e0 $BC\/\/EF$ (theo c\u00e2u 1)<br\/> $\\Rightarrow O_2O_3\/\/BC$ <br\/> M\u1eb7t kh\u00e1c: $OO_1\\bot BC$ <br\/> $\\Rightarrow OO_1 \\bot O_2O_3$ <br\/> Do v\u1eady, g\u00f3c t\u1ea1o b\u1edfi hai \u0111\u01b0\u1eddng th\u1eb3ng $O_1O$ v\u00e0 $O_2O_3$ l\u00e0 $90^o$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $90$. <\/span><\/span> "}]}],"id_ques":1429},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho b\u1ed1n c\u00e2u","temp":"fill_the_blank","correct":[[["O"]]],"list":[{"point":10,"width":20,"type_input":"","ques":"<span class='basic_left'> Cho $\\Delta ABC$, $O$ l\u00e0 giao \u0111i\u1ec3m c\u1ee7a c\u00e1c \u0111\u01b0\u1eddng trung tr\u1ef1c c\u1ee7a ba c\u1ea1nh. G\u1ecdi $O_1; O_2; O_3$ theo th\u1ee9 t\u1ef1 l\u00e0 c\u00e1c \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng v\u1edbi \u0111i\u1ec3m $O$ qua c\u00e1c c\u1ea1nh $BC, CA$ v\u00e0 $AB$. <br\/><br\/> <b> C\u00e2u 4:<\/b> Tr\u1ef1c t\u00e2m c\u1ee7a $\\Delta O_1O_2O_3$ l\u00e0 \u0111i\u1ec3m _input_ <\/span> ","explain":" V\u1ebd h\u00ecnh <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai5/lv3/img\/H815_K1_3.jpg' \/><\/center> <span class='basic_left'> Theo c\u00e2u 3, ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c: $OO_1 \\bot O_2O_3$ <br\/> Ch\u1ee9ng minh t\u01b0\u01a1ng t\u1ef1, ta c\u00f3: $OO_3 \\bot O_1O_2$ <br\/> X\u00e9t trong $\\Delta O_1O_2O_3$ c\u00f3: $OO_3\\cap OO_1=O$ <br\/> Do \u0111\u00f3: $O$ l\u00e0 tr\u1ef1c t\u00e2m c\u1ee7a $\\Delta O_1O_2O_3$ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $O$. <\/span><\/span> "}]}],"id_ques":1430}],"lesson":{"save":0,"level":3}}

Điểm của bạn.

Câu hỏi này theo dạng chọn đáp án đúng, sau khi đọc xong câu hỏi, bạn bấm vào một trong số các đáp án mà chương trình đưa ra bên dưới, sau đó bấm vào nút gửi để kiểm tra đáp án và sẵn sàng chuyển sang câu hỏi kế tiếp

Trả lời đúng trong khoảng thời gian quy định bạn sẽ được + số điểm như sau:
Trong khoảng 1 phút đầu tiên + 5 điểm
Trong khoảng 1 phút -> 2 phút + 4 điểm
Trong khoảng 2 phút -> 3 phút + 3 điểm
Trong khoảng 3 phút -> 4 phút + 2 điểm
Trong khoảng 4 phút -> 5 phút + 1 điểm

Quá 5 phút: không được cộng điểm

Tổng thời gian làm mỗi câu (không giới hạn)

Điểm của bạn.

Bấm vào đây nếu phát hiện có lỗi hoặc muốn gửi góp ý