1. The problem statement, all variables and given/known data Alrighty. I have reduced a vibrations problem to an integral and I am having some trouble evaluating it. I have a value for t and need to find: [tex]-c\omega^2Z^2\int_0^t\cos^2(\omega t-\phi)\ dt[/tex] (1) I guess it is just my memory that is the problem. If I had [itex]\int\cos^2(x)\ dx[/itex] It would not be a problem. I am thinking now that I type this that a simple U substitution should do the trick right? EDIT: If I let [itex]u=\omega t-\phi\ \Rightarrow du=\omega\ dt[/itex] So (1) becomes: [tex]-c\omega Z^2\int_0^t\cos^2u\ du[/tex] Yes?