cho tu giac ABCD co goc A =a ,C=b . hai duong thang AD va BC cat nhau tai E ,hai duong thang ABva DC cat nhau tai F . Cac tia phan giac cua hai goc AEB va AFDcat nhau tai I .tINH goc EIF theo a,b
cho tu giac ABCD co A=a,C=b.Hai duong thang AD va BC cat nhau tai E,hai duong thang AB va DC cat nhau tai F.Cac tia phan giac cua hai goc AEB va AFD cat nhau tai I.Tinh goc EIF theo a,b
CÓ VẼ HÌNH NHÉ
1. Cho hinh thang ABCD , phan giac cua goc A cat duong cheo BD tai E va phan giac goc B cat AC tai F . Chung minh EF //AB?
2.Cho tam giac ABC , cac tia phan giac cua goc B va goc C cat nhau tai O . Tu A ve duong thang vuong goc voi OA cat BO , CO lan luot tai M va N . Chung minh BM vuong goc voi BN , CM vuong goc voi CN?
3.Cho goc vuong xOy ,vaf tam giac ABC vuong tai A (B thuoc Ox ,AC thuoc Oy,A va O nam tren hai nua mat phang doi nhau co bo la BC ).chung minh OA la tia phan gic cua xOy ?
cac ban giup mik nha
cho tu giac abcd biet goc a: goc b: goc c: goc d =4:3:2:1
a) tinh cac goc cua tu giac abcd
b) cac tia phan giac cua goc c va goc d cat nhau tai e. cac duong phan giac cua goc ngoai tai ca dinh c va d cat nhau tai f. tinh goc ced va goc cfd
a) Ta có: \(\frac{\widehat{A}}{4}=\frac{\widehat{B}}{3}=\frac{\widehat{C}}{2}=\frac{\widehat{D}}{1}\)
Áp dụng t/c dãy tỉ số bằng nhau ta được:
\(\frac{\widehat{A}}{4}=\frac{\widehat{B}}{3}=\frac{\widehat{C}}{2}=\frac{\widehat{D}}{1}=\frac{\widehat{A}+\widehat{B}+\widehat{C}+\widehat{D}}{4+3+2+1}=\frac{360}{10}=36\)
\(\Rightarrow\widehat{A}=144^0;\widehat{B}=108^0;\widehat{C}=72^0;\widehat{D}=36^0\)
cho 2 duong thang xy//mn ,duong thang A cat 2 duong thang xy va mn lan luot tai A va B. ke tia phan giac cua foc xAB va phan giac cua goc ABM chung cat nhau tai C. Ke tia phan giac cua BAI va tia phan giac cua ABN chung cat nhau tai D.chung minh: a)AC vuong goc voi AD, BD vuong goc voi BC
cho 2 duong thang xy//mn ,duong thang A cat 2 duong thang xy va mn lan luot tai A va B. ke tia phan giac cua foc xAB va phan giac cua goc ABM chung cat nhau tai C. Ke tia phan giac cua BAI va tia phan giac cua ABN chung cat nhau tai D.chung minh: a)AC vuong goc voi AD, BD vuong goc voi BC
Cho tu giac ABCD biet so do cua cac goc A ,B,C,D ti le thuan voi5,8,13,10 .a, Tinh so do cac goc cua tu giac ABCD . b, Keo dai hai canh AB va DC cat nhau o E , keo dai hai canh AD va BC cat nhau o F . Hai tia phan giac cua cac goc AED va goc AFB cat nhau o O . phan giac cua goc AFB cat cac canh CD va AB tai M va N . Chung minh O la trung diem cua doan MN
CAC BAN GIUP MINH VOI MINH CAN GAP
Cho tu giac ABCD co O la giao diem cac tia phan giac cua cac goac C va D
a Ting COD biet goc A bang 120 ggoc B bang 90
b Tinh Cod theo A va B
cCac tia phan gia cua cac goc A va B cat nhau tai I va cat cac tia phan giac cac goc C va D thu tu tai E va F. C/m rang tu giac OEIF co cac goc doi bu nhau
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cho tam giac ABC vuong tai A, duong phan giac trong cua goc B va gocC cat nhau tai I. Duong thang di qua C vuong goc voi BI cat AB tai D. cho AB=5, IC= can bac hai cua 6, TINH BC
Cho tam giac ABC co A=75, B=35. AD la tia phan giac cua goc A. Qua A ke duong vuong goc voi AD duong thang nay cat uong thang BC tai E. Tren nua mat phang bo AE cung phia voi C ve tia Ax sao cho AEC=EAx. Tia Ax cat ED tai M.
a) Chung minh: ME=MD
b) Chung minh: BC= chu vi tam giac ABC
c) Tu M; N ta ke cac duong thang lan luot vuong goc voi Ae; AM. Chung cat nhau tai O. Duong thang OC cat AE tai N va AD tai K.Chung minh MN vuong goc voi NK