f(x)=2(sinx,cosx)·(cosx,-cosx)+|(sinx,cosx)|
(sinx,cosx)·(cosx,-cosx)=sinxcosx-cosxcosx
=1/2sin2x-(cos2x+1)/2
=1/2sin2x-1/2cos2x-1/2
=√2/2sin(2x-π/4)-1/2
|(sinx,cosx)| =√(sin^2x+cos^2x)=1
所以f(x)=2(sinx,cosx)·(cosx,-cosx)+|(sinx,cosx)|
=√2sin(2x-π/4)-1+1=√2sin(2x-π/4)谢谢啦😘😝嗯，没事！