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Question
In triangle ABC; AB = AC and ∠A : ∠B = 8 : 5; find angle A.
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Solution
Let ∠A = 8x and ∠B = 5x
Given: AB = AC
⇒ ∠B = ∠C = 5x ...[Angles opp. to equal sides are equal]
Now,
∠A + ∠B + ∠C = 180°
⇒ 8x + 5x + 5x = 180°
⇒ 18x = 180°
⇒ x = 10°
Given that :
∠A = 8x
⇒ ∠A = 8 x 10°
⇒ ∠A = 80°.
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