若sin(pai＋a)＋cos(pai/2＋a)＝-m,则cos(3pai/2-a)＋2sin(2pai-a)的值为?

sin(π＋α) = -sinα
cos(π/2＋α)=-sinα
sin(π＋α)＋cos(π/2＋α) = -m
-sinα-sinα = -m
sinα=m/2
cos(3π/2-α)＋2sin(2π-α)
= -sinα - 2sinα
= -3sinα
= -3*m/2
= -3m/2