cho 3 duong thang phan biet abc biet a vuong goc c va b vuong goc c thi
neu hai duong thang a va b phan biet cung vuong goc voi duong thang MN thi chung......voi nhau
A.song song
B.vuong goc
C.cat nhau
D.trung nhau
hai duong thang a va b vuong goc voi nhau tai o qua o ve duong thang a vuong goc voi b thi a va a' la hai duong thang phan biet hay trung nhau tai sao ?
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
cho hai duong thang xx' va yy' cat nhau tai O
a) cm hai tia phan giac Ot , Ot' cua mot cap goc ke bu tao thanh mot goc vuong
b)cm neu M thuoc duong thang Ot' thi M cach deu hai duong thang xx' va yy'
c) cm neu M cach deu hai duong thang xx' va yy' thi M thuoc duong thang Ot hoac thuoc duong thang Ot'
d)Khi M=O thi cac khoang cach tu M den xx' va yy' bang bao nhieu
e)em co nhan xet gi ve tap hop cac diem cach deu hai duong thang cat nhau xx' va yy'
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 duong phan giac BD va CE cat nhau tai I . Tren canh BC lay M sao cho BM = BE . a) Chung minh tam giac MID can
b) ve duong thang vuong goc voi BI tai B va vuong goc voi CI tai C , chung cat nhau o K . CMR : 3 diem A,I,K thang hang
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 vuong tai A, duong cao AH , phan giac ID.goi I, J lan luot la giao diem cac duong phan giac cua tam giac ABH, ACE; E la giao diem cua duong thang BI va ẠJ. C/m: a, tam giac ABE vuong b, IJ vuong goc voi AD