、对角矩阵是对称矩阵
若<img src、"http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/1/image241.png" alt="" align="middle">均为零矩阵，则有<img src="http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/1/image249.png" alt="" align="middle">
若<img src、"http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/1/image250.png" alt="" align="middle">，且<img src="http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/1/image251.png" alt="" align="middle">，则<img src="http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/1/image252.png" alt="" align="middle">
若<img src、"http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/1/image253.png" alt="" align="middle">，<img src="http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/1/image254.png" alt="" align="middle">，则<img src="http://oss.ouchn.cn/ddzx/N601/gongxue/jjsx/img/1/image255.png" alt="" align="middle">