f(x)=sin²(x+5pai/4),
=(1-cos(2x+5pai/2))/2
=(1+sin2x)2
=1/2+1/2sin2x
lg3和lg1/3 互为相反数
所以 又sin(-x)=-f(x)
所以 a+b=1Ϊʲô (1-cos(2x+5pai/2))/2=(1+sin2x)2 �����յ���ʽ cos(2x+5pai/2))=-sin2x