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.
Chung to rang neu hai duong thang song song thi cac tia phan giac cua moi cap goc dong vi song song voi nhau.
CMR : neu 1 dg thang cat 2 dg thang song song thi 2 tia phan giac cua 1 cap goc dong vi song song voi nhau
a) duong thang c co vuong goc voi duong thang b ko vi sao
b)cho doan thang d cat 2 duong thang a va b tai A va B cho niet goc A1= 115do . Tinh so do cac goc B2,B3,A3
c)goi AX va By lan luot la tia phan giac cua cac goc A1 va B CHUNG MINH Ax song song By
1)So vo duoc thuong cua 3 lop 7A ;7B ; 7C lan luot ti le voi 2;3;4 .Tinh so vo moi lop biet rang so vo cua lop 7A va 7c nhieu hon so vo cua lop 7B la 36 quyen
2) cho tam giac co goc abc = 60do;goc ACB=50do.Goi AD la tia phan giac goc BAC[D thuoc BC]
a)Tinh goc BAC;goc ADc
b)Qua B ke duong thang d song song voi AD ,d cat duopng thang AC tai M.Chung minh goc MBA = goc BMA
c)Goi Ax la tia phan giac cua goc BAM.Chung minh Ax vuong goc voi BM
cho tam giac ABC co goc ACB bang 60 do .
a) ve tam giac ABC
b) hai tia phan giac cua goc ABC va ACB cat nhau tai I . Qua I ve duong thang song song Bc , duong thang nay cat cac duong thang AB va AC tai D v E .Tinh so do goc ACI va goc CIE
c) So sanh 2 goc DIB va ABI
d) Qua A ke AH vuong goc voi BC tai H , qua C ke CK vuong goc voi DE tai K .Giai thic vi sao AH song song voi CK
e) tinh so do goc CAH
GIAI NHANH GIUM MINH NHA!!!MINH DANG CAN GAP ...
Cho biet tu diem A thuoc tia phan giac cua goc xoy co mu nha! ve duong thang song song voi Ox cat Oy tai B va ve duong thang song song voi Oy tai C a)chung minh BOA=AOC ,b) chung minh AO la tia phan giac cua BAC
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
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
cho tam giac abc vuong tai a co db la duong phan giac ke ae vuong goc voi bd [e thuoc bd ] ae cat bc o k hay chung minh dieu nay nhe +chung minh tam giac abk can +chung minh dk vuong goc voi bc +ke ah vuong goc voi bc chung minh ak la tia phan giac cua goc hac +goi i la giao diem cua ah va bd chung minh ik song song voi ac
