<p>矩形截面挖去一个边长为a的正方形，如图所示，该截面对z轴的惯性矩Iz为：<img alt="" src="https://file.gaojiufeng.cn/learnAppQuestion/5b/b9/5bb965ca6f493ae4d69e6b005fc1f86c.jpg" style="width: 100%;height: auto;"><img alt="" src="https://file.gaojiufeng.cn/learnAppQuestion/72/d4/72d4f99b2cb656fdf3c9e8ea7d44a2dd.jpg" style="width: 100%;height: auto;"></p>