sinα=-3/5,则cos2α=?
问题描述:
sinα=-3/5,则cos2α=?
答
cos2α=1-2sin^2a=1-2(-3/5)^2=1-18/25=7/25
答
cos2α=1-2(sinα)^2=1-2*(-3/5)^2=7/25.
答
解
cos2α=1-2sin^2a=1-2(-3/5)^2=1-18/25=7/25