## 编译环境 操作系统 * [* ] Windows 7/8/10 * [ ] macOS * [ ] Linux `若需勾选，请把[ ]改成[x]` Tex发行版 * [* ] TexLive `年份` * [ ] MikTeX `版本号` * [ ] CTeX `若需勾选，请把[ ]改成[x]` ## 我的问题 在此输入你遇到的问题... 如何改为两倍行间距的同时使得有大括号的公式上下方空格较小？ ``` \documentclass{article} \usepackage{geometry} \renewcommand{\baselinestretch}{2.0} \usepackage{bm,amsfonts,amssymb,amsmath,float}\usepackage{sectsty} \begin{document} Portfolio optimization aims to obtain an investment with low risk and high return by distributing money among candidate securities. \begin{equation} f(\alpha) = \left\{ \begin{array}{cl} 2\alpha +3, & \text{if} \ \alpha < 0.5 \\ 4\alpha +2, & \text{if} \ \alpha \geq 0.5, \\ \end{array} \right. \end{equation} Markowitz first proposed mean-variance model into portfolio optimization by minimizing variance to reduce volatility. \end{document} ```