In triangle ABC, external angle at vertex B = 120; angle ACB = 70. Find: the degree measure of external angle at vertex A
| April 14, 2021 | education
The outer angle is equal to the sum of the other two angles of the triangle, that is, A + C = 120 °, hence the angle A = 120 ° – 70 ° = 50 °.
The outer angle and the angle of the triangle are adjacent angles, so the outer angle at angle A is 180 ° – 50 ° = 130 °.
Answer: the outer angle at the vertex A is 130 °.
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