In triangle ABC, angle C is 50 degrees, AC = BC. Find the degree measure of the outer angle at the vertex B.
| September 16, 2021 | education
The ABC triangle is isosceles, since AC = BC. The angles at the base of an isosceles triangle are equal, so ∠ A = ∠ B. The sum of the angles in any triangle is 180 °. That’s why:
∠ А + ∠ В = 180 ° – ∠ С = 180 ° – 50 ° = 130 °;
∠ B = 130 ° / 2 = 65 °;
Outside apex angle B = 180 ° – 65 ° = 115 °.
Answer: 115 °
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