、对称矩阵是对角矩阵
若<img src、"http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/3-3/image023.png" alt="" align="middle">均为零矩阵，则有<img src="http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/3-3/image034.png" alt="" align="middle">
若<img src、"http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/3-3/image031.png" alt="" align="middle">，<img src="http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/3-3/image032.png" alt="" align="middle">，则<img src="http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/3-3/image033.png" alt="" align="middle">
若<img src、"http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/3-3/image035.png" alt="" align="middle">为可逆矩阵，且<img src="http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/3-3/image036.png" alt="" align="middle">，则<img src="http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/3-3/image037.png" alt="" align="middle">