Originally Posted by
skeeter the Fundamental Theorem of Calculus ...
$\displaystyle u$ and $\displaystyle v$ are both functions of $\displaystyle x$
$\displaystyle \frac{d}{dx} \left[ \int_v^u f(z) \, dz \right] = f(u) \cdot \frac{du}{dx} - f(v) \cdot \frac{dv}{dx}$