1+cos2x1+\cos 2x1+cos2x
1−cos2x1-\cos 2x1−cos2x
=12(1+cos2x)=\frac{1}{2}(1+\cos 2 x)=21(1+cos2x)
=12(1−cos2x)=\frac{1}{2}(1-\cos 2 x)=21(1−cos2x)