如：y=(sinx+cosx)^2+2cos^2x
=sin^2x+2sinxcosx+cos^2x+2cos^2x
=1+sin2x+2cos^2x
=1+sin2x+2*(1+cos2x)2
=1+sin2x+1+cos2x
=2+√2sin(2x+45°)
三角函数怎么转化为y=Asin(wx+φ)的形式
如：y=(sinx+cosx)^2+2cos^2x
=sin^2x+2sinxcosx+cos^2x+2cos^2x
=1+sin2x+2cos^2x
=1+sin2x+2*(1+cos2x)2
=1+sin2x+1+cos2x
=2+√2sin(2x+45°)