Question

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

Answer 1

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