Fourier basis
= Fourier basis
On the circle of circumference $2\pi$, the functions $e_k(x)=e^{ikx}$ for $k\in\mathbb Z$ form an orthogonal basis of $L^2$.
= Fourier basis
On the circle of circumference $2\pi$, the functions $e_k(x)=e^{ikx}$ for $k\in\mathbb Z$ form an orthogonal basis of $L^2$.