Question

若tan(兀-α)=2,则2sin(3兀+α)cos(5/2兀+α)+sin(3/2兀-α)sin(兀-α)=?

Answer 1

因为：tan(π-a)=2,所以：tana=-2

2sin(3π+a)cos(5/2π+a）+sin(3/2π-a)sin(π-a)

=+2sinasina-cosasina=[2(sina)^2-sinacosa]/[(sina)^2+(cosa)^2]

=[2(tana)^2-tana]/[(tana)^2+1]

=[2(-2)^2-(-2]/[(-2)^2+1]=2