sin阿拉法等于二分之根号三求cos2阿拉法的值

2025-12-15 05:44:19
推荐回答(2个)
回答1:

由已知sina=根号3/2得sin^2a=3/4,cos^2a=1/4
cos2a=cos^2a-sin^2a=-1/2

回答2: