(2)分子拆开=√2(sin2α/√2-cos2α/√2)+1=sin2α-cos2α+1=2sinαcosα-[(cosα)^2-(sinα)^2]+(cosα)^2+(sinα)^2=2sinαcosα+2(sinα)^2=2sinα(sinα+cosα)=(4/3)sinα
分母=1+tanα=1+sinα/cosα=(sinα+cosα)/cosα=(2/3)/cosα
原式=2sinαcosα
注意4/9=(sinα+cosα)^2=(sinα)^2+(cosα)^2+2sinαcosα=1+2sinαcosα
2sinαcosα=4/9-1=-5/9
注：^2表示平方