Respuesta :

It follows from

[tex]\cos2x=\cos(x+x)=\cos x\cos x-\sin x\sin x=\cos^2x-\sin^2x=1-2\sin^2x[/tex]

[tex]\implies\cos 2x-1=-2\sin^2x[/tex]

[tex]\implies\sin^2x=\dfrac{1-\cos2x}2[/tex]