1.3sin(a+b-a)=sin(a+b+a) ,
3[sin(a+b)cosa-cos(a+b)sinA]=sin(a+b)cosa+cos(a+b)sina
2sin(a+b)cosa=4cos(a+b)sinA
tan(a+b)=2tana
2.f(x)=(1-tanx)(1+sin2x+cos2x)-3,"代表平方
=1+sin2x+cos2x+
(sinx/cosx)(sinx"+cosx"+2Sinxcosx+cosx"-sinx")-3
=sin2x+cos2x+2sinxcosx+2sinx"-2
=2sin2x-1
略