# How does the fundamental theorem of calculus connect derivatives and integrals?

(I) $\frac{d}{\mathrm{dx}} {\int}_{a}^{x} f \left(t\right) \mathrm{dx} = f \left(x\right)$
(II) $\int f ' \left(x\right) \mathrm{dx} = f \left(x\right) + C$