Answer
\[
\int_{0}^{\pi / 2}\left(\sin ^{2} x\right) d x
\]
Work Step by Step
Replace the sum with an integer sign with the limits $a$ and $b, \Delta x_{k}$ with $d x$, and $x_{k}^{*}$ with $x$.
\[
\int_{0}^{\pi / 2}\left(\sin ^{2} x\right) d x
\]