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

\parindent=0pt

QUESTION

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

\bigskip

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}
