The function is periodic with period π.

So, we conclude that the Fourier series will have even harmonics, and will be of the form:

a₀/2 + (a₂ cos 2t + b2 sin 2t) + (a₄ cos 4t + b₄ sin 4t) + (a₆ cos 6t + b₆ sin 6t) + ...