{"segment":[{"part":[{"title":"\u0110i\u1ec1n \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["70"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H8110_K1_1.jpg' \/><\/center> Cho h\u00ecnh thoi nh\u01b0 h\u00ecnh tr\u00ean. <br\/> T\u00ednh $\\widehat{ABC}$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $\\widehat{ABC}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ ","explain":"<span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H8110_K1_1.jpg' \/><\/center> Theo h\u00ecnh v\u1ebd: $\\widehat{BCA}=55^o$ <br\/> M\u00e0 $AB=BC$ (gi\u1ea3 thi\u1ebft) <br\/> $\\Rightarrow \\Delta ABC$ c\u00e2n t\u1ea1i B <br\/> $\\Rightarrow \\widehat{ABC}+2\\widehat{BCA}=180^o$ <br\/> $\\Rightarrow \\widehat{ABC}=180^o-2\\widehat{BCA}$ <br\/> $\\Rightarrow \\widehat{ABC}=180^o-2.55^o=70^o$ <br\/> <span class='basic_pink'> Do \u0111\u00f3 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $70$ <\/span><\/span> "}],"id_ques":1551},{"title":"\u0110i\u1ec1n \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["20"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H8110_K1_2.jpg' \/><\/center> Cho h\u00ecnh vu\u00f4ng nh\u01b0 h\u00ecnh tr\u00ean. <br\/> Bi\u1ebft $BD=5\\sqrt{2}\\, (cm)$ <br\/> T\u00ednh chu vi h\u00ecnh vu\u00f4ng $ABCD$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$ cm ","Hint":" T\u00ednh \u0111\u1ed9 d\u00e0i c\u1ea1nh c\u1ee7a h\u00ecnh vu\u00f4ng khi bi\u1ebft \u0111\u01b0\u1eddng ch\u00e9o.","explain":"<span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H8110_K1_2.jpg' \/><\/center> X\u00e9t tam gi\u00e1c vu\u00f4ng $ABD$ c\u00f3: $BD=5\\sqrt{2}\\, cm$ <br\/> \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pi - ta - go v\u00e0o $\\Delta ABD$: <br\/> $AB^2+AD^2=BD^2$ <br\/> $\\Rightarrow 2AB^2=BD^2$ <br\/> $\\Rightarrow 2AB^2=(5\\sqrt{2})^2$ <br\/> $\\Rightarrow 2AB^2=50$ <br\/> $\\Rightarrow AB^2=25 \\Rightarrow AB=5\\, (cm)$. <br\/> Chu vi h\u00ecnh vu\u00f4ng $ABCD$ l\u00e0: $4.5=20\\, (cm)$. <br\/> <span class='basic_pink'> Do \u0111\u00f3 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $20$. <\/span><\/span> "}],"id_ques":1552},{"title":"\u0110i\u1ec1n \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["1"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"<span class='basic_left'> C\u00e1c \u0111i\u1ec3m $A', B', M'$ l\u1ea7n l\u01b0\u1ee3t \u0111\u1ed1i x\u1ee9ng v\u1edbi c\u00e1c \u0111i\u1ec3m $A, B, M$ qua \u0111i\u1ec3m $O$. Bi\u1ebft \u0111i\u1ec3m $M$ n\u1eb1m gi\u1eefa c\u00e1c \u0111i\u1ec3m $A$ v\u00e0 $B$ v\u00e0 $MB=4,5\\, cm; A'B'=5,5\\, cm$. T\u00ednh \u0111\u1ed9 d\u00e0i $AM$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $AM=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}$ (cm) ","explain":"<span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H8110_K1_3.jpg' \/><\/center> Do $A', B'$ \u0111\u1ed1i x\u1ee9ng v\u1edbi c\u00e1c \u0111i\u1ec3m $A, B$ qua \u0111i\u1ec3m $O$ n\u00ean: $AB=A'B'=5,5\\, (cm)$ <br\/> Theo b\u00e0i: $M$ n\u1eb1m gi\u1eefa $A$ v\u00e0 $B$. <br\/> $\\Rightarrow$ Ba \u0111i\u1ec3m $M, A, B$ th\u1eb3ng h\u00e0ng. <br\/> $\\Rightarrow AM+MB=AB$ <br\/> Thay s\u1ed1: $AM +4,5=5,5$ <br\/> $\\Rightarrow AM=5,5-4,5$ <br\/> $\\Rightarrow AM=1\\, (cm)$. <br\/> <span class='basic_pink'> Do \u0111\u00f3 ph\u1ea3i \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $1$. <\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> 1. Hai \u0111i\u1ec3m $A, B$ \u0111\u1ed1i x\u1ee9ng v\u1edbi c\u00e1c \u0111i\u1ec3m $A', B'$ qua \u0111\u01b0\u1eddng th\u1eb3ng d th\u00ec $AB=A'B'$. <br\/> 2. C\u00e1c \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng v\u1edbi c\u00e1c \u0111i\u1ec3m kh\u00e1c th\u1eb3ng h\u00e0ng qua m\u1ed9t \u0111i\u1ec3m th\u00ec ch\u00fang c\u0169ng th\u1eb3ng h\u00e0ng. <\/i><\/span> "}],"id_ques":1553},{"title":"H\u00e3y ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":"<span class='basic_left'> Cho h\u00ecnh thang c\u00e2n c\u00f3 m\u1ed9t trong c\u00e1c g\u00f3c b\u1eb1ng $60^o$ v\u00e0 c\u00e1c \u0111\u00e1y c\u00f3 \u0111\u1ed9 d\u00e0i $15\\, cm$ v\u00e0 $49\\, cm$. Chu vi h\u00ecnh thang c\u00e2n \u0111\u00f3 l\u00e0: <\/span> ","select":["A. $128\\, cm$","B. $130\\, cm$","C. $132\\, cm$ ","D. $134\\, cm$"],"hint":" T\u00ecm \u0111\u1ed9 d\u00e0i c\u1ea1nh b\u00ean c\u1ee7a h\u00ecnh thang c\u00e2n r\u1ed3i t\u00ednh chu vi c\u1ee7a h\u00ecnh thang c\u00e2n.","explain":"<span class='basic_left'> H\u00ecnh thang c\u00e2n c\u00f3 m\u1ed9t trong c\u00e1c g\u00f3c l\u00e0 $60^o$ th\u00ec c\u00f3 m\u1ed9t g\u00f3c kh\u00e1c l\u00e0 $120^o$. <br\/> Ta c\u00f3 h\u00ecnh v\u1ebd nh\u01b0 sau: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H8110_K1_4.jpg' \/><\/center> K\u1ebb t\u1eeb hai \u0111\u1ec9nh $A$ v\u00e0 $B$ c\u00e1c \u0111\u01b0\u1eddng vu\u00f4ng g\u00f3c v\u1edbi \u0111\u00e1y $CD$, c\u1eaft $CD$ l\u1ea7n l\u01b0\u1ee3t t\u1ea1i $H$ v\u00e0 $K$. <br\/> Khi \u0111\u00f3 ta d\u1ec5 d\u00e0ng ch\u1ec9 ra \u0111\u01b0\u1ee3c: $AB=HK=15\\, (cm)$ v\u00e0 $DH=CK=\\dfrac{49-15}{2}=17\\, (cm)$. <br\/> X\u00e9t $\\Delta ADH$ c\u00f3 $\\widehat{D}=60^o$ n\u00ean $AD=2DH=34\\, (cm)$. <br\/> Do \u0111\u00f3: $AD=BC=34\\, (cm)$. <br\/> Chu vi h\u00ecnh thang c\u00e2n l\u00e0: <br\/> $AB+2AD+DC$$=15+2.34+49=132\\, (cm)$. <br\/> <span class='basic_pink'> V\u1eady ch\u1ecdn \u0111\u00e1p \u00e1n C. <\/span><\/span> ","column":4}],"id_ques":1554},{"title":"H\u00e3y ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":"<span class='basic_left'> Cho $\\Delta ABC$ vu\u00f4ng t\u1ea1i $A\\, (AB < AC)$. G\u1ecdi $I$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $BC$. Qua $I$ v\u1ebd $IM \\bot AB$ t\u1ea1i $M$ v\u00e0 $IN\\bot AC$ t\u1ea1i $N$. <br\/><br\/> <b> C\u00e2u a: <\/b> G\u1ecdi $D$ l\u00e0 \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng v\u1edbi $I$ qua $N$. T\u1ee9 gi\u00e1c $ADCI$ l\u00e0 h\u00ecnh g\u00ec? <\/span> ","select":["A. H\u00ecnh b\u00ecnh h\u00e0nh","B. H\u00ecnh ch\u1eef nh\u1eadt","C. H\u00ecnh thoi","D. H\u00ecnh vu\u00f4ng"],"explain":"<span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H8110_K1_5a.jpg' \/><\/center> Do $I$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $BC$ n\u00ean $AI$ l\u00e0 \u0111\u01b0\u1eddng trung tuy\u1ebfn c\u1ee7a $\\Delta ABC$ vu\u00f4ng t\u1ea1i $A$. <br\/> $\\Rightarrow AI=IC=BI=\\dfrac{1}{2}BC$ (t\u00ednh ch\u1ea5t \u0111\u01b0\u1eddng trung tuy\u1ebfn \u1ee9ng v\u1edbi c\u1ea1nh huy\u1ec1n trong tam gi\u00e1c vu\u00f4ng). <br\/> Do \u0111\u00f3 $\\Delta AIC$ c\u00e2n. <br\/> M\u00e0 $IN$ l\u00e0 \u0111\u01b0\u1eddng cao n\u00ean c\u0169ng l\u00e0 trung tuy\u1ebfn, t\u1ee9c l\u00e0: $NA=NC$ <br\/> L\u1ea1i c\u00f3: $NI=ND$ (t\u00ednh ch\u1ea5t \u0111\u1ed1i x\u1ee9ng). <br\/> $\\Rightarrow ADCI$ l\u00e0 h\u00ecnh b\u00ecnh h\u00e0nh (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft). <br\/> H\u01a1n n\u1eefa: $IN\\bot AC$ t\u1ea1i $N$ <br\/> $\\Rightarrow AC\\bot ID$ <br\/> $\\Rightarrow ADCI$ l\u00e0 h\u00ecnh thoi (d\u1ea5u hi\u1ec7u nh\u1eadn bi\u1ebft). <br\/> <span class='basic_pink'> V\u1eady ch\u1ecdn \u0111\u00e1p \u00e1n C. <\/span><\/span> ","column":2}],"id_ques":1555},{"title":"H\u00e3y ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"<span class='basic_left'>Cho $\\Delta ABC$ vu\u00f4ng t\u1ea1i $A\\, (AB < AC)$. G\u1ecdi $I$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $BC$. Qua $I$ v\u1ebd $IM \\bot AB$ t\u1ea1i $M$ v\u00e0 $IN\\bot AC$ t\u1ea1i $N$. <br\/><br\/> <b> C\u00e2u b: <\/b> \u0110\u01b0\u1eddng th\u1eb3ng $BN$ c\u1eaft $DC$ t\u1ea1i $K$. Khi \u0111\u00f3 \u0111\u1ed9 d\u00e0i c\u1ea1nh $DC$ g\u1ea5p m\u1ea5y l\u1ea7n \u0111\u1ed9 d\u00e0i $DK$? <\/span> ","select":["A. $2$","B. $3$","C. $4$","D. $2,5$"],"explain":"<span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H8110_K1_5b.jpg' \/><\/center> K\u1ebb qua $I$ \u0111\u01b0\u1eddng th\u1eb3ng song song v\u1edbi $BK$ c\u1eaft $CD$ t\u1ea1i $E$. <br\/> X\u00e9t $\\Delta BCK$ c\u00f3: $BI=IC; IE \/\/BK$ <br\/> $\\Rightarrow EC=KE$. (1) <br\/> X\u00e9t $\\Delta IDE$ c\u00f3: $NI=ND; NK \/\/ IE$. <br\/> $\\Rightarrow EK=DK$ (2) <br\/> T\u1eeb (1) v\u00e0 (2) $\\Rightarrow DC=3DK$. <br\/> <span class='basic_pink'> V\u1eady ch\u1ecdn \u0111\u00e1p \u00e1n B. <\/span><\/span> ","column":4}],"id_ques":1556},{"title":"H\u00e3y ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"<span class='basic_left'> Cho h\u00ecnh ch\u1eef nh\u1eadt c\u00f3 chu vi $84\\, cm$. Hi\u1ec7u kho\u1ea3ng c\u00e1ch t\u1eeb giao \u0111i\u1ec3m c\u1ee7a \u0111\u01b0\u1eddng ch\u00e9o \u0111\u1ebfn c\u1ea1nh l\u1edbn h\u01a1n v\u1edbi kho\u1ea3ng c\u00e1ch t\u1eeb giao \u0111i\u1ec3m \u0111\u00f3 \u0111\u1ebfn c\u1ea1nh nh\u1ecf h\u01a1n l\u00e0 $6\\, cm$. \u0110\u1ed9 d\u00e0i hai c\u1ea1nh k\u1ec1 h\u00ecnh ch\u1eef nh\u1eadt l\u00e0: <\/span> ","select":["A. $5\\, cm$ v\u00e0 $26\\, cm$","B. $15\\, cm$ v\u00e0 $27\\, cm$","C. $14\\, cm$ v\u00e0 $30\\, cm$","D. $13\\, cm$ v\u00e0 $29\\, cm$"],"explain":"<span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H8110_K1_6.jpg' \/><\/center> G\u1ecdi kho\u1ea3ng c\u00e1ch t\u1eeb giao \u0111i\u1ec3m hai \u0111\u01b0\u1eddng ch\u00e9o \u0111\u1ebfn hai c\u1ea1nh l\u00e0 $a$ v\u00e0 $b$ ( $a > b$) $(cm)$ <br\/> \u0110\u1ed9 d\u00e0i hai c\u1ea1nh k\u1ec1 c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt l\u00e0: $2a$ v\u00e0 $2b$ $(cm)$ <br\/>N\u1eeda chu vi c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt l\u00e0: <br\/> $2a+2b=84:2=42\\, (cm)$ <br\/> $\\Rightarrow a+b=21\\, (cm)$ <br\/> Theo b\u00e0i, ta c\u00f3: <br\/> $\\begin{aligned} & \\left\\{ \\begin{aligned} & a+b=21 \\\\ & a-b=6 \\\\ \\end{aligned} \\right. & \\Rightarrow \\left\\{ \\begin{aligned} & 2a=27 \\\\ & 2b=15 \\\\ \\end{aligned} \\right. \\\\ \\end{aligned}$ <br\/> \u0110\u1ed9 d\u00e0i hai c\u1ea1nh k\u1ec1 c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt l\u00e0: $15\\, cm$ v\u00e0 $27\\, cm$. <br\/> <span class='basic_pink'> V\u1eady ch\u1ecdn \u0111\u00e1p \u00e1n B. <\/span><\/span> ","column":2}],"id_ques":1557},{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["150"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho g\u00f3c nh\u1ecdn $\\widehat{xOy}=75^o$. Cho \u0111i\u1ec3m $M$ thu\u1ed9c mi\u1ec1n trong c\u1ee7a g\u00f3c $xOy$ sao cho $\\widehat{MOx}=60^o$. K\u1ebb $ME\\bot Ox; MF\\bot Oy$. \u0110i\u1ec3m $A$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $OM$. Tia ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $\\widehat {EAF}$ c\u1eaft $EF$ \u1edf $H$. <br\/><br\/> <b> C\u00e2u a:<\/b> T\u00ednh $\\widehat{EAF}$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $\\widehat{EAF}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}^o$ <\/span> ","Hint":" $\\widehat{EAF}=\\widehat{EAM}+\\widehat{MAF}$.","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H819_K1_4.jpg' \/><\/center> X\u00e9t t\u1ee9 gi\u00e1c $OEMF$ c\u00f3: <br\/> $\\widehat{EOF}+\\widehat{OEM}+\\widehat{EMF}+\\widehat{OFM}=360^o$ (\u0111\u1ecbnh l\u00ed t\u1ed5ng c\u00e1c g\u00f3c trong t\u1ee9 gi\u00e1c). <br\/> $\\Rightarrow \\widehat{EMF}=360^o- (\\widehat{EOF}+\\widehat{OEM}+\\widehat{OFM})$<br\/> $\\widehat{EMF}=360^o-(75^o+90^o+90^o)$ <br\/> $\\widehat{EMF}=105^o$ <br\/> Do $\\Delta OMF$ vu\u00f4ng t\u1ea1i $F$ v\u00e0 $OA=MA$ n\u00ean $OA=AF$. <br\/> $\\Rightarrow \\Delta OAF$ c\u00e2n t\u1ea1i $A$. <br\/> $\\Rightarrow \\widehat{F_1}=\\widehat{O_2}$. <br\/> Theo gi\u1ea3 thi\u1ebft: $\\widehat{MOx}=\\widehat{O_1}=60^o \\Rightarrow \\widehat{MOy}=\\widehat{O_2}=15^o$. <br\/> X\u00e9t trong $\\Delta OAF$ c\u00f3 $\\widehat{MAF}$ l\u00e0 g\u00f3c ngo\u00e0i \u0111\u1ec9nh $A$ n\u00ean: <br\/> $\\widehat{MAF} =2\\widehat{O_2}=30^o$ (1) <br\/> T\u01b0\u01a1ng t\u1ef1, ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c $\\Delta OAE$ c\u00e2n t\u1ea1i $A$. <br\/> $\\Rightarrow \\widehat{O_1}=\\widehat{E_1}$. <br\/> X\u00e9t $\\Delta OAE$ c\u00f3 $\\widehat{EAM}$ l\u00e0 g\u00f3c ngo\u00e0i \u0111\u1ec9nh $A$ n\u00ean: <br\/> $\\widehat{EAM}=2\\widehat{O_1}=120^o$. (2) <br\/> T\u1eeb (1) v\u00e0 (2): $\\widehat{EAF}=\\widehat{EAM}+\\widehat{MAF}$$=120^o+30^o=150^o$. <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $150$. <\/span> <\/span> "}],"id_ques":1558},{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang ho\u1eb7c sai","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":" <span class='basic_left'> Cho g\u00f3c nh\u1ecdn $\\widehat{xOy}=75^o$. Cho \u0111i\u1ec3m $M$ thu\u1ed9c mi\u1ec1n trong c\u1ee7a g\u00f3c $xOy$ sao cho $\\widehat{MOx}=60^o$. K\u1ebb $ME\\bot Ox; MF\\bot Oy$. \u0110i\u1ec3m $A$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $OM$. Tia ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $\\widehat {EAF}$ c\u1eaft $EF$ \u1edf $H$. <br\/><br\/> <b> C\u00e2u b:<\/b> Ta ch\u1ee9ng minh \u0111\u01b0\u1ee3c $AH\\bot EF$. <\/span>","select":[" \u0110\u00fang"," Sai"],"explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H819_K1_4.jpg' \/><\/center> Theo c\u00e2u a, ta \u0111\u00e3 ch\u1ec9 ra \u0111\u01b0\u1ee3c: $AE=AF=OA$ <br\/> $\\Rightarrow \\Delta EAF$ c\u00e2n t\u1ea1i $A$. <br\/> M\u00e0 theo gi\u1ea3 thi\u1ebft, $AH$ l\u00e0 ph\u00e2n gi\u00e1c c\u1ee7a g\u00f3c $\\widehat{EAF}$ n\u00ean c\u0169ng l\u00e0 \u0111\u01b0\u1eddng cao t\u1eeb \u0111\u1ec9nh $A$ trong $\\Delta EAF$. <br\/> $\\Rightarrow AH \\bot EF$. <br\/> <span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0: \u0110\u00fang <\/span><\/span> ","column":2}],"id_ques":1559},{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["8"],["6"],["4"]]],"list":[{"point":10,"width":40,"type_input":"","ques":"<span class='basic_left'> Cho $\\Delta ABC$ c\u00f3 chu vi l\u00e0 $36\\, cm$. G\u1ecdi $M, N, P$ l\u1ea7n l\u01b0\u1ee3t l\u00e0 trung \u0111i\u1ec3m c\u1ee7a c\u00e1c c\u1ea1nh $AB, BC$ v\u00e0 $CA$. Bi\u1ebft $AB:BC:CA=2:3:4$. T\u00ednh \u0111\u1ed9 d\u00e0i c\u00e1c c\u1ea1nh c\u1ee7a $\\Delta MNP$. <br\/><br\/> <b> \u0110\u00e1p \u00e1n: <\/b> $\\left\\{ \\begin{align} & MN=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{} \\, (cm) \\\\ & MP=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\, (cm) \\\\ & NP=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\, (cm) \\\\ \\end{align} \\right. $ <\/span> ","Hint":" T\u00ednh \u0111\u1ed9 d\u00e0i c\u00e1c c\u1ea1nh c\u1ee7a $\\Delta ABC$ r\u1ed3i suy ra \u0111\u1ed9 d\u00e0i c\u00e1c c\u1ea1nh $\\Delta MNP$.","explain":" <span class='basic_left'> <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai10/lv3/img\/H8110_K1_7.jpg' \/><\/center> Theo b\u00e0i: $AB:BC:CA=2:3:4$ <br\/> $\\Rightarrow \\dfrac{AB}{2}=\\dfrac{BC}{3}=\\dfrac{CA}{4}$ <br\/> \u00c1p d\u1ee5ng t\u00ednh ch\u1ea5t d\u00e3y t\u1ec9 s\u1ed1 b\u1eb1ng nhau,ta \u0111\u01b0\u1ee3c: <br\/> $\\dfrac{AB}{2}=\\dfrac{BC}{3}=\\dfrac{CA}{4}$$=\\dfrac{AB+BC+CA}{2+3+4}$$=\\dfrac{36}{9}=4$ <br\/> $\\Rightarrow \\left\\{ \\begin{aligned} & AB=8\\, (cm) \\\\ & BC=12\\, (cm) \\\\ & CA=16\\, (cm) \\\\ \\end{aligned} \\right. $ <br\/> M\u00e0 $M, N, P$ l\u1ea7n l\u01b0\u1ee3t l\u00e0 trung \u0111i\u1ec3m c\u1ee7a c\u00e1c c\u1ea1nh $AB, BC$ v\u00e0 $CA$. <br\/> $\\Rightarrow MN, NP, MP$ l\u00e0 c\u00e1c \u0111\u01b0\u1eddng trung b\u00ecnh c\u1ee7a $\\Delta ABC$. <br\/> $\\Rightarrow \\left\\{ \\begin{aligned} & MN=\\dfrac{AC}{2}=\\dfrac{16}{2}=8\\, (cm) \\\\ & MP=\\dfrac{BC}{2}=\\dfrac{12}{2}=6\\, (cm) \\\\ & NP=\\dfrac{AB}{2}=\\dfrac{8}{2}=4\\, (cm) \\\\ \\end{aligned} \\right. $ <br\/> <span class='basic_pink'> V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0: $MN=8\\, cm$; $MP=6\\, cm$; $NP=4\\, cm$. <\/span> <\/span> "}],"id_ques":1560}],"id_ques":0}],"lesson":{"save":1,"level":3,"time":44}}