勾股定理是初中几何中的一个极为重要的定理，它在数学解题中有着广泛的应用．本文举例说明勾股定理在几何证题中的应用．例1如图1，在△ABC中，AB=AC，BDAC于D．求证：分析在Rt△BDC和Rt△ADB中，由勾股定理，得于是，要证结论成立，只要证即可．这只要经过适当的恒等变形即得 The Pythagorean theorem is an extremely important theorem in the geometry of junior high school. It has a wide range of applications in mathematical problem solving. This paper illustrates the application of the Pythagorean theorem in geometrical proofs. Example 1 is shown in Fig. 1. In △ ABC, AB = AC, and BDAC is in D. Proof: analysis in Rt △ BDC and Rt △ ADB, from the Pythagorean theorem, so in order to prove the conclusion of the agreement, as long as the card can be. This will only have to pass the appropriate constant deformation.