问题圆内接四边形的两条对角线互相垂直,试证该四边形的对边平方和等于定值.自己试一试,如果思维陷入困境,再读下面的.已知条件很清楚,而结论中的“定值”等于多少,题中并未说明.如果能先把这个“定值”寻求到,问题就趋于明朗化,解题就有了方向.方法是从特殊情况获取信息.这里 The two diagonals of the question circle inscribed in the quadrilateral are perpendicular to each other. Try to prove that the quadratic sum of squares of the quadrilateral is equal to the fixed value. Try it for yourself. If the thinking is in trouble, read the following again. The known conditions are clear, and the conclusion The “value” in Chinese is not stated in the question. If we can seek this “value” first, the problem becomes clear and the problem has its direction. The method is to obtain information from a special situation.