In a ΔABC, if AB = AC and ∠B = 70°. Find ∠A.
Question:

In a ΔABC, if AB = AC and ∠B = 70°. Find ∠A.

 

Solution:

Consider a ΔABC, if AB = AC and ∠B = 70°

Since, AB = AC ΔABC is an isosceles triangle

∠B = ∠C [Angles opposite to equal sides are equal]

∠B = ∠C = 70∘

And also,

Sum of angles in a triangle = 180°

∠A + ∠B + ∠C = 180°

∠A + 70° + 70° = 180°

∠A = 180° – 140°

∠A = 40°

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