In a triangle ABC AC = BC. the outside angle at apex B is 122 degrees. Find corner C.

1. We calculate the angle ABC, taking into account that it is equal to the difference between the magnitude of the expanded angle and the external angle at the vertex B:
Angle ABC = 180 ° – 122 ° = 58 °.
2. Triangle ABC is isosceles, since according to the condition of the problem the side of the AC of the triangle is equal to the side of the AC. Therefore, each of the angles at side AB is 58 °.
3. Considering that the sum of the inner angles of the triangle is 180 °, we calculate the value of the angle C:
Angle C = 180 ° – 58 ° – 58 ° = 64 °.
Answer: angle C = 64 °.