NẾU SINA=3/5, SINB=8/17 0   THÌ COS(A+B) BẰNG

Question

Câu 416: Nếu sina=3/5, sinb=8/17  0   thì cos(a+b) bằng: a  2 b a) 36/85 b) -36/85 c) 84/85 d) -84/85  

Answer

a) 36/85 b) -36/85 c) 84/85 d) -84/85