<p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">根号的特性就是这样,正常的情形下,根号里面的内容高度过高时,根号会由斜转值,甚至是倾斜的角度会换方向,如果你需要强制的左倾斜根号,可以这么干</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\documentclass{ctexart}</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\usepackage{newtxmath}</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\let\sqrt\undefined</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\DeclareSymbolFont{yh}{OMX}{yhex}{m}{n}</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\DeclareMathRadical{\sqrtsign}{symbols}{"70}{yh}{"70}</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\makeatletter</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\DeclareRobustCommand\sqrt{\@ifnextchar[\@sqrt\sqrtsign}</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\makeatother</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\begin{document}</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\[\sqrt{\sum_{j=1}^m}\sqrt[3]{\sum_{j=1}^m}\]</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, "><br></p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">\end{document}</p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, "><img src="https://wenda.latexstudio.net/data/ueditor/php/upload/image/20190825/1566708404870934.png" title="1566708404870934.png" alt="QQ截图20190825124633.png" width="326" height="184"></p><p style="box-sizing: content-box; margin-top: 10px; margin-bottom: 10px; padding: 0px; line-height: 1.8; font-size: 14px; word-break: break-word; color: rgb(40, 40, 40); font-family: -apple-system, ">不过老实说,newtxmath的求和符号也很丑</p><p><br></p>