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In a triangle ABC, AB = AC, ∠BAC = 40° then the external angle at B is :
Answer & Solution
Correct Answer:
Option
C
According to question,
Given :
∠A = 40° AB = AC
∴ ∠B = ∠C
In ΔABC
∠A + ∠B + ∠C = 180°
40° + 2∠B = 180°
2∠B = 180° - 40°
2∠B = 140°
∠B = 70°
∴ External angle at B = 180° - 70° = 110°
Given :
∠A = 40° AB = AC
∴ ∠B = ∠C
In ΔABC
∠A + ∠B + ∠C = 180°
40° + 2∠B = 180°
2∠B = 180° - 40°
2∠B = 140°
∠B = 70°
∴ External angle at B = 180° - 70° = 110°
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