I currently try to understand Baxter's solution of the 2D-Ising-Model using the 'commuting transfermatrix method' and I have the following problem:
I want to express the function $$ F(j) = ln\left[ 2*\left(\cosh(2A)\cdot \cosh(2B) + \frac{ \sqrt{ 1 + k^2 - 2k \cdot \cos( \frac{\pi j}{2p})}}{k}\right)\right] $$ in a Fourier series of the form $$ F(j) = \sum_{m=0}^{\infty} a_m \cdot \cos(2m \cdot \frac{\pi j}{2p}) $$ and determine the Fourier coefficients $ a_m $ . The variables A and B are general complex numbers, p is a constant integer and k is a positive real number.
I tried to calculate the coefficients using the command FourierTransform[] in Mathematica but the only output I received was the input itself.