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 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 tam giac ABC co goc A=a . Cac tia phan giac cua goc B va C cat nhau tai I . Cac tia phan giac cua cac goc ngoai ding B va C cat nhau tai K. Tia phan giac cua g oc B cat tia phan giac ngoai ding C tai E. Tinh so do cua BKC, B . C theo a
Cho tam giac AOB tren tia doi cua tia OAlay diem C sao choOA=OC. tren tia doi cua tia OB, lay diem D sao cho OD=OB. cac tia phan giac cac goc O,C,D va O,B,A cat nhau o E . tia phan giac goc O,A, B cat BE tai F. CMR
a) tam giac AOB=tam giac COD
b)AB\\OD ; AD\\BC ; CE\\AF
c)^CEB bang nua tong 2 goc ^CAB va ^CDB
Cho tu giac ABCD co goc A-goc B=50 do .Cac tia phan giac cua goc C va goc D cat nhau tai I va goc CID=115 do. Tinh cac goc A va B
Cho tu giac ABCD co A = 1000 , B = 1200 , cac tia phan giac cua C va D cat nhau tai E
a) Tinh goc CED
b) Cac tia phan giac cua goc ngoai tai dinh C va D cat nhau tai F. Chung minh: CED + CFD = 1800
cho tam giac ABC co A=60 cac tia phan giac cua goc B va C cat nhau tai I,cat cac canh AC,AB lan luot tai D vaE tia phan gia cua goc BIC cat BC o F tinh goc BIC
Cho tu giac ABCD co goc A = 1000, B = 1200 , cac tia phan giac cua goc C va D cat nhau tai E.
a) Tinh CED
b) Cac tia phan giac cua goc ngoai tai dinh C va D cat nhau tai F. Chung minh: \(\widehat{CED}+\widehat{CFD}=180^0\)
Cho tam giac ABC, goc A bang 60 dọ. Tia phan giac trong cua goc B va goc C cat cac canh doi dien tai D va E, BD va CE cat nhau o O. Tia phan giac cua goc BOC cat BC tai F. CM:
a) OD=OE=OF
b) tam giac DEF deu
