\documentclass[12pt]{jsarticle}
\usepackage{amsmath,amssymb}
\pagestyle{empty}
\begin{document}
\setlength{\baselineskip}{22pt}
\begin{flushleft}
{\huge 3}
　正の数$\theta_1$，$\theta_2$，$\theta_3$，$\theta_4$，$\theta_5$が
$\theta_1+\theta_2+\theta_3+\theta_4+\theta_5=2\pi$を満たしながら変わるとき
\[ \sin\theta_1+\sin\theta_2+\sin\theta_3+\sin\theta_4+\sin\theta_5 \]
の最大値を，次の手順で求めよ．
\begin{description}
\item[(1)]$\alpha<2\pi$を満たす正の数$\alpha$を決める．
$\theta_1+\theta_2=\alpha$のとき，
$\sin\theta_1+\sin\theta_2$の最大値を求めよ．
\item[(2)]$\beta<2\pi$を満たす正の数$\beta$を決める．
$\theta_1+\theta_2+\theta_3+\theta_4=\beta$のとき，
$\sin\theta_1+\sin\theta_2+\sin\theta_3+\sin\theta_4$の最大値を$\theta_5$で表せ．
\item[(3)]$\sin\theta_1+\sin\theta_2+\sin\theta_3+\sin\theta_4+\sin\theta_5$の最大値を求めよ．
\end{description}
\end{flushleft}
\end{document}
