Suppose $f : [a, b] \to \R$ is integrable, and define $F : [a, b] \to \R$ by $$F(t) = \int_a^t f(x)\,dx.$$ Then $F$ is continuous at $t_0 \in (a, b)$...
Suppose $f : [a, b] \to \R$ is integrable, and define $F : [a, b] \to \R$ by $$F(t) = \int_a^t f(x)\,dx.$$ Then $F$ is differentiable at $t_0 \in (a, b)$...