## Thomas' Calculus 13th Edition

$\int_0^1 \sqrt {4-x^2}$
Interpreting Limits of sums as Integrals -$\lim\limits_{||p|| \to 0}$ $\Sigma^n_{k=1} \sqrt {4-c_k^2}$ where P is a partition of [0,1] as -- $\int_0^1 \sqrt {4-x^2}$