Triangle ABC is isosceles, AC-base. The angle at the vertex B is 120 degrees. Find the degree measures

Triangle ABC is isosceles, AC-base. The angle at the vertex B is 120 degrees. Find the degree measures of the outer angles of the triangle.

The angles of a triangle add up to 180 °.

In an isosceles triangle, the angles at the base are equal. 180 ° – 120 ° = 60 °;

60 °: 2 = 30 °. Angles at the base of 30 degrees.

Outer apex angle B = 180 ° -120 ° = 60 °;

external angles at the vertices A and C 180 ° – 30 ° = 120 °.

Answer: 60 °, 120 °, 120 °.