已知sin(α-3π)+cos(π/2+α)=m,求cos(α-7π/2)+2sin(2kπ-α)的值
问题描述:
已知sin(α-3π)+cos(π/2+α)=m,求cos(α-7π/2)+2sin(2kπ-α)的值
答
sin(α-3π)+cos(π/2+α)=m,
-sinα-sinα=m
所以:sinα=-m/2
cos(α-7π/2)+2sin(2kπ-α)
=-sinα-2sinα
=-3sinα
=3m/2