在初中数学教科书(九年级(下),华东师大第三版)第82页,有这样一道习题:“一组对边相等,一组对角相等的四边形是否一定是平行四边形?如果一定是,请给出证明;如果不一定是,请举出反例.”我们知道,满足上述题设条件的凸四边形不一定是平行四边形.但是,所能见到的构造其反例的方法却 In junior high school mathematics textbooks (ninth grade (below), East China Normal University, third edition) on page 82, there is such a problem: “A set of equal sides, a set of diagonal equal quadrilateral must be parallelogram? If yes, give proof; if not necessarily, give a counterexample. ”We know that the convex quadrilateral that satisfies the above conditions does not have to be a parallelogram, but the counter-examples we can see of constructing it