简答题:<img src="http://www.weimei168.com/uploads/202208/161258450965461.png" width="533" height="74" /> <br /> 求：(1)<img src="http://www.weimei168.com/uploads/202208/161258451734591.png" width="17" height="19" />的值； <br /> (2)正交矩阵Q和对角矩阵A，使得Q <img src="http://www.weimei168.com/uploads/202208/161258452453981.png" width="14" height="25" />AQ=A．