Basic Way to Prove That Two Angles Are Equal

Abstract

Proving that two angles are equal plays an important role in junior high school geometry and is one of the basic problem types. After learning about isosceles triangles, students in the second year of junior high school can summarize and generalize to know that there are several basic ways to prove that two angles are equal: (1) Use the properties of intersecting lines or parallel lines; (2) Use the same angle (or equal angle) ) of the complementary angles (or supplementary angles) are equal; (3) use the properties of congruent triangles; (4) use the properties of isosceles triangles or equilateral triangles; (5) use the determination theorem of angle bisector. Example 1 As shown in Figure 1, it is known that AB-AC, AH-AE, CH, BE are interlinked E. Proof: AF bisects zBAC analysis to prove that AF bisects fBAf7<=/1-'32<-convex ABF, convex ACF or convex AHFM, convex AEF, --BF-CF or DF'-EF, convex BDFed convex CEF<=BD 1CE, /31/4 are known to be easy to obtain BD-CE, and it is not difficult to prove that convex A