Hi everyone,

I, for the life of me, can't seem to figure this one out. It's from the GRE math subject test.

Let $\displaystyle f(x) = \int_{0}^{x} \frac{cos(xt)}{t}dt$.

Then, find $\displaystyle f'(x)$

If we could pull out the $\displaystyle x$ from the integral, then it's just product rule and FTC. But that $\displaystyle x$ is tied up in there.

Any ideas from the calculus geniuses out there?