I have to find the first (at least the first) term of the Fourier expansion of the following function: $$f(t)=a^\alpha|\cos(\Omega t+b)|^\alpha sgn(\cos(\Omega t+b))$$ where $a$ is a real and positive constant, $b$ a real constant and $\alpha$ un real in $]0;2[$. $\Omega = 2\pi f_0 = 2\pi/T$ with $T$ the period.
What annoys me is this power $\alpha$ which is not necessarily an integer. I don't know how to tackle the problem.