Answer:
![\angle B\cong \angle C](https://img.qammunity.org/2020/formulas/mathematics/high-school/3a261o1ciw8jk8ss33chw5p68cpx0ptg7w.png)
Explanation:
We are given that
![AB\cong AC](https://img.qammunity.org/2020/formulas/mathematics/high-school/turmy8uy8oc8ktlvr7dud5pxd68hyr3gs5.png)
We have to prove that
![\angle B\cong \angle C](https://img.qammunity.org/2020/formulas/mathematics/high-school/3a261o1ciw8jk8ss33chw5p68cpx0ptg7w.png)
![AB\cong AC](https://img.qammunity.org/2020/formulas/mathematics/high-school/turmy8uy8oc8ktlvr7dud5pxd68hyr3gs5.png)
Therefore, AB=AC
Suppose , angle B and angle C are not congruent.
Then, the measure of one angle is greater than the other.
If
![m\angle B > \angle C](https://img.qammunity.org/2020/formulas/mathematics/high-school/92t9ex9eki9cl1e8yhyldx1q5990kuyy7c.png)
Then ,
![AC > AB](https://img.qammunity.org/2020/formulas/mathematics/high-school/bm9jeqmryq2cb9qiz4758i7z9h8864ymku.png)
By using triangle parts theorem
It states that when an angle is greater than other then opposite side of greater angle is greater than the opposite side of other angle.
If
![m\angle B < m\angle C](https://img.qammunity.org/2020/formulas/mathematics/high-school/jh9lrbu76nahed8mg0nswwtfo4v3jzt5ge.png)
Then, AC < AB.
It is contradiction because we are given AB=AC.
Therefore, it can be concluded that
![\angle B\cong \angle C](https://img.qammunity.org/2020/formulas/mathematics/high-school/3a261o1ciw8jk8ss33chw5p68cpx0ptg7w.png)