Cho 5 duong thang tren mat phang trong do khong co 2 duong thang nao song song. Chung to rang trong 5duong thang do ton tai hai tao voi nhau mot goc nho hon hoac bang 36 do
cho 9 duong thang trong do khong co 2 duong thang nao song song chung minh rang it nhat cung co 2 duong thang ma goc nhon giua chung khong nho hon 20 do
tren 1 mat phang cho 7 dg thang . trong do ko co 2 dg thang nao song song . chung minh co it nhat 2 dg thang cat nhau theo 1 goc nho hon 260
cho 9 duong thang trong do khong co 2 duong thang nao song song . chung minh rang it nhat cung co 2 duong thang magoc nhon giua chung ko nho hon 20
Cho 2 duong thang AB cat boi duong thang c tai A va B . Cho biet tong 2 goc trong cung phia bu nhau voi 1 goc sole trong voi 1 trong 2 goc nay bang 300 do va trong 2 goc ke bu co 1 goc nay gap doi goc kia . Hai duong thang A va B co song song voi nhau khong vi sao
Cho \(\Delta ABC\)co goc A=90 do. Duong thang AH vuong goc voi BC tai H. Tren duong vuong goc voi BC tai B lay diem D khong cung nua mat pahng bo BC voi diem A sao cho AH=BD
a/ Chung minh \(\Delta AHB=\Delta DBH\)
b/ Hai duong thang AB va DH co song song khong? Tai sao?
c/ Tinh goc ACB, biet BAH=35 do
cho 2 diem A va B nam tren 2 nua mat phang doi nhau bo la duong thang xx' tren duong thang xx' lay 1 diem M bat ki biet rang goc xMB = goc x'MA. Chung minh rang 3 diem A M B thang hang
cho goc xoy =50 do. lay diem A tren tia ox . tren cung 1 nua mat phang bo ox chua tia oy, ve tia ot sao cho oy cat nhau tai B va goc oAt =80 do. goi at' la tia phan giac cua goc xAt
a) chung minh At'song song voi Oy
b) tren nua mat phang ko chua diem A bo duong thang oy ve tia Bn song song Ox
cho 9 duong thang trong do khong co 2 duong thang nao song song. CMR it nhat cung co 2 duong thang ma goc nhon giua chung khong nho hon 600