Find the angles of an isosceles triangle if one of the angles at the base is a) 50 °; b) 70 °; c) 39 °; d) 83 °
| September 21, 2021 | education
An isosceles triangle is a triangle in which the sides are equal, as well as the angles at the base are equal:
AB = BC;
∠А = ∠С.
Since the sum of all the angles of the triangle is 180º, then:
∠А + ∠В + ∠С = 180º;
∠В = 180º – ∠А – ∠С.
a) ∠В = 180º – 50º – 50º = 80º.
Answer: ∠А = ∠С = 50º; ∠В = 80º.
b) ∠В = 180º – 70º – 70º = 40º.
Answer: ∠А = ∠С = 70º; ∠В = 40º.
c) ∠В = 180º – 39º – 39º = 102º.
Answer: ∠А = ∠С = 39º; ∠В = 102º.
d) ∠В = 180º – 83º – 83º = 14º.
Answer: ∠А = ∠С = 83º; ∠В = 14º.
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