g(x) = [tex] \pi - 2x[/tex] (fog)(x) = sin2x f(x) = ......?

[tex]\displaystyle \pi-2x=a\\2x=\pi-a\\\\(f\circ g)(x)=\sin2x\\f(g(x))=\sin2x\\f(\pi-2x)=\sin2x\\f(a)=\sin(\pi-a)\\f(a)=\sin a\\\boxed{\boxed{f(x)=\sin x}}[/tex]