cos(X减二分之派)等于多少.怎么做的

2025-04-24 18:43:26
推荐回答(1个)
回答1:

cos(X-π/2)
公式:cos(A-B) = cosAcosB+sinAsinB
=cosx cos(-π/2)+sinx sin(-π/2)
=cosx*0+sinx*(-1)
=-sinx