<p><br><img src="https://img.jishulink.com/201906/imgs/16315d45d79241588a589297e7fa081a.jpg" data-mobile-src="https://img.jishulink.com/201906/imgs/16

<p>三点圆弧，画个大概的样子，然后约束一下，再标草图尺寸。</p>