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 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 tam giac abc co b>c.duong thang chua tian p/g cua goc ngoai dinh a cat bc o d.cm

adb=1/2(b-c)

tu b ve duong thang// ad. cm tam giac abe co 2 goc bang nhau

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.

tam giac ABC co tia phan giac cua goc B cat AC o D qua A ke duong thang song song voi BD duong thang nay cat duong thang BC o E hay chung to rang goc BAE=goc BEA

CO AI GIAI NHANH HO MINH VOI

tam giac ABC co tia phan giac cua goc B cat AC o D.Qua A ke duong thang song song voi BD,duong thang nay cat duong thang BC o E.Chung minh rang goc BEA = goc BAE

Cho 1 duong thang cat 2 duong thang song song,Hay chung minh rang:

a,Cac tia phan giac cua 1 cap goc so le (hoac so le ngoai thi song song voi nhau

b,Cac tia phan giac cua 1 cap goc dong vi thi song song voi nhau.

c,Cac tia phan giac cua 1 cap goc trong cung phia(hoac ngoai cung phia) thi vuong goc voi nhau.

cho tam giac ABC co BC=4cm. tren tia doi cua tia BC lay diem D sao cho BD=2cm/ a, tinh do dai CD; b,goi M la chung diem cua CD.tinh do dai BM;c,biet goc DAC bang 112 do .Ãxtia phan giac cua goc BAC va goc BAD. tinh so do goc xAy;d, tren nua mat phang bo la duong thang AC co chua diem D neu ve them n tia goc A phan biet khong trung voi cac tia ÂC,Ã,AB,Ay,AD thi co tat ca bao nhieu goc dinh A va Ay thu tu la