In an isosceles triangle ABC with base AC, the outer angle at apex A is 140 degrees. Find the angles of triangle ABC.

The sum of the outer angle at the vertex A and the inner angle A of the triangle ABC is equal to 180 ° (adjacent angles)

1) Find the angle A:

A = 180 ° – 140 °;

A = 40 °

2) In an isosceles triangle, the angles at the base are equal, which means

C = A = 40 °

3) The sum of the angles in the triangle is 180 °, we can find the angle B:

A + B + C = 180 °

B = 180 ° – A – C;

B = 180 ° – 40 ° – 40 °;

B = 100 °

The angles of the ABC triangle are 40 °, 100 °, 40 °, respectively.