trong cac khang dinh sau khang dinh nao dung A)2 tia chung goc la 2 tia doi nhau B)2 duong thang phan biet thi k co diem chung C)neu M la trung diem cua doan thang AB thi MA=MB D)co it nhat 1 duong thang di qua 2 diem A va B
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1/ đúng
2/ đúng
3/sai thiếu điều kiện M,A,B thẳng hàng
cho tam giác ABC có ab<ac
kẻ AD là phân giác góc A, kẻ DI sao cho AI = AB
ta có tam giác ABD= tam giácAID (c.g.c)
=>góc B = AID (tương ứng )
Mà AID = góc C +IDC (góc ngoài tam giác IDC )
=>góc AID > góc C hay góc B > góc C
b) tương tự câu a
c) dựa theo tính chất đường trung bình của 1 tam giác là đường nối trung điểm của hai cạnh bất kì và // , =1/2 cạnh còn lại
ta vẽ góc :
a)ta có góc mon = 900
b)==> 750
còn lại bạn tụ giải nha
đến giờ ăn cơm rồi
Câu C
Đúng nhất !!!