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
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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 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 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
1.cho tam giac ABC co goc B-C=alpha phan giac AD
a) tinh gocADC,ADB theo alpha
b)Ve duong cao AH tinh goc HAD
2.chotam giac ABC,gocA =alpha,cac tia ohan giac cua B va C cat nhay tai I.Phan giac cat goc ngoai tai dinh B,C cat nhau tai K.Tia p/g goc B cat goc ngoai o dinh C.tinh cac goc BIC,BKC,BEC theo alpha.
Cho tam giac ABC .Cac duong thang chua tia phan giac cua cac goc ngoai dinh B va o dinh C cat nhau tai K.Tinh goc a biet goc BCK =50°
CHO tam giac ABC co goc A = 60 do .Cac tia phan giac cua B va C cat nhau tai O va cat AC ,AB lan luot tai D va E .Tia phan giac cua goc BOC cat tai BC tai F .CMR : a. OE=OD=OF . b. Tam giac DEF đêu
CHO TAM GIAC ABC CAC TIA PHAN GIAC CUA GOC B VA C CAT NHAU TAI I CHUNG MINH AI LA TIA PHAN GIAC CUA GOC A
Cho tam giac ABC co goc A khac goc B cac tia phan giac trong va ngoai cua goc C lan luot cat duong thang BA tai D va E tinh goc CED theo goc A va goc B cua tam giac ABC
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: \(\widehat{CED}+\widehat{CFD}=180^0\)