ABC is an isosceles triangle, AB = AC, angle B = 50 °. Find angle A and angle C.

Since, by condition, an isosceles triangle ABC is given, in which AB = AC, then the base in this triangle is BC.
According to the rule, in an isosceles triangle, the angles at the base are equal.
That is, angle B is equal to angle C.
By condition, it is given that the angle B = 50 °.
Hence, it is possible to write down.
B = C = 50 °.
Now let’s find the angle A.
According to the rule, the sum of the values of all angles in a triangle is 180 °.
Thus, we will write.
A + B + C = 180 °.
A + 50 ° + 50 ° = 180 °.
A + 100 ° = 180 °.
A = 180 ° – 100 °.
A = 80 °.
Answer: A = 80 °; C = 50 °.