m=(cosA,sinA),向量n=(2,-1),且向量m×向量n=0
∴2cosA-sinA=0
∴tanA=sinA/cosA=2
∴f(x)=cos2x+tanAsinx
=cos2x+2sinx
=1-2(sinx)^2+2sinx
=-2(sinx-1/2)^2+3/2.
∵sinx∈[-1,1]
∴f(x)∈[-3,3/2]
m=(cosA,sinA),向量n=(2,-1),且向量m×向量n=0
∴2cosA-sinA=0
∴tanA=sinA/cosA=2
∴f(x)=cos2x+tanAsinx
=cos2x+2sinx
=1-2(sinx)^2+2sinx
=-2(sinx-1/2)^2+3/2.
∵sinx∈[-1,1]
∴f(x)∈[-3,3/2]