化简:y=2sinxsin(x-π/2)+cos²x-sin²x
问题描述:
化简:y=2sinxsin(x-π/2)+cos²x-sin²x
答
f(x)=-2sinxcosx+cos2x
=sin2x+cos2x
=√2(√2/2sin2x+√2/2cos2x)
=√2sin(2x+π/4)请问下,为什么是-4分之π不是+呢???sinAcosB+sinBcosA=sin(A+B)