Theorem 7.3 Class 9 Maths Explanation with Proof

In this post, we will discuss theorem 7.3 class 9 Maths which is related to Chapter 7 Triangles Class 9 Mathematics. After understanding theorem 7.3, you can solve the exercise questions given in the NCERT book of Class 9 Maths.

Theorem 7.3 Class 9

The sides opposite to equal angles of a triangle are equal.

Given 

∆ABC in which 

∠B=∠C 

To prove  

AC=AB

Construction 

Draw the bisector of ∠A and let it intersect BC at D.

Proof

In ∆ACD and ∆ABD, we have

∠2=∠1 (by construction)

∠C=∠B (given)

AD=AD (common)

So, ∆ACD ≅∆ABD (AAS congruence rules)

Hence, AC=AB

Related Topics 

1. Theorem 7.2

2. Theorem 7.4