tren duong thang b lay 3 diem A , B ,C . biet AB = 8 cm , BC = 4 cm . goi M ,N ,P lan luot la trung diem cua cac doan thang AB , AC , BC , chung to rang cac doan thang MN va AP co cung trung diem

cho 3 diem A,B,C biet AB=1,8cm AC=1,3cm BC=3cm .Ba diem A,B,C co diem nao thang hang khong ? Vì sao

Cho 4 diem A,B,C,D .Biet rang ba diem B,C,D thang hang,ba diem B,A,C  thang hang.Hoi 3 diem B,A,D  co thang hang ko?Vi sao?

giup minh voi a

Tks

tren duong thang xy cho truoc lay 4 diem theo thu tu A,B,C,D biet AB=2cm,BC=5cm,AD=9cm

a,Tinh AC

b,Tinh CD

c, so sanh do dai doan AC voi doan BC

d, chung to rang trung diem cua AD trung voi trung diem doan BC

Cho tam giac ABC. Duong thang qua B song song voi AC cat duong thang qua C song song voi AB tai D

a) Chung minh rang tu giac ABDC la hinh binh hanh

b) Goi M la trung diem canh BC. Chung minh rang 3 diem A,M,D thang hang

Lam day du nhe

cho 4 diem A, B, C, D phan biet cu qua 2 diem ta ve dc 1 duong thang . Hoi ve duoc bao nhiu duong thang biet rang trong 4 diem phan biet ko co 3 diem nao thang hang

Cho 4 diem A,B,C,D theo thu tu do tren mot duong thang va AB=CD=3; BC=5. Hay chung to rang:

a, AC=BD

b, Hai doan thang BC va AD co cung mot trung diem.(ve hinh ra nhe)

cho 3 diem A,B,C thang hang biet AB=5 cm ,BC=2cm .tinh AC

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