# In triangle ABC, sides AB and BC are equal. What is the angle adjacent to angle C

September 14, 2021 | education

| **In triangle ABC, sides AB and BC are equal. What is the angle adjacent to angle C, if it is known that the angle adjacent to angle A is 121?**

Since AB and BC are equal in a triangle, angles A and C are also equal (property of an isosceles triangle).

The angle adjacent to the angle A is equal to 180 ° – ∠A.

The angle adjacent to the angle С is equal to 180 ° – ∠С.

Since the angles A and C are equal, then the angles adjacent to them are equal. Means,

∠С = 121 °.