\documentclass[a4paper,12pt]{article}
\newcommand\ds{\displaystyle}
\begin{document}

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QUESTION

Evaluate $\ds\int_0^\frac{\pi}{2}\sin(2x)\,dx$.


ANSWER

$\ds\int_0^\frac{\pi}{2}\sin(2x)\,dx
=\left[-\frac{\cos(2x)}{2}\right]_0^\frac{\pi}{2}
=-\frac{1}{2}\{\cos\pi-\cos0\} =-\frac{1}{2}(-1-1) =1$




\end{document}