Originally Posted by

**matyoun89** Hi everyone,

My problem is to do with calculating the fourier coefficients $\displaystyle C_k$ of $\displaystyle x(t)=cos(2t)$,

where $\displaystyle C_k = {1 \over T} \int_0^Tx(t)e^{-j\omega_0kt} dt$ where $\displaystyle k \in \bold Z$ and $\displaystyle \omega_0 = 2 \to T = \pi$

Everytime I try to evaluate the integral by letting $\displaystyle cos(2t) = {1 \over 2}(e^{j2t} + e^{-j2t})$ I get $\displaystyle C_k = 0$ which I am sure is incorrect as the fourier series of $\displaystyle cos(2t) \not= 0$. If some one could show me the working to this problem so I can compare it with mine to see where I am going wrong it would be greatly appreciated.