sinα=-3/5,则cos2α=?

问题描述:

sinα=-3/5,则cos2α=?

cos2α=1-2sin^2a=1-2(-3/5)^2=1-18/25=7/25

cos2α=1-2(sinα)^2=1-2*(-3/5)^2=7/25.


cos2α=1-2sin^2a=1-2(-3/5)^2=1-18/25=7/25