Integral with functions as limit How can I solve integrals like this :
$$
\int_{g(x)}^{f(x)} u(t) dt
$$
I think it has a general formula to solve it. Thanks for your help.

This isn't any different as solving without functions in as limits, just find an antiderivative
$$U(t) = \int u(t)dt$$
and plug in your limits:
$$
\int_{g(x)}^{f(x)} u(t) dt = U(f(x))-U(g(x))
$$
