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in a triangle ABC, BC=AB and angle B=80 degrees, Then find the measure of angle A 

Dear Students,

Given : BC = AB

⇒∠A = ∠C                 ................ (1)   (Angle opposite to equal sides are equal)
Now,
⇒∠A + ∠B + ∠C = 180             (Angle Sum property)
⇒∠A + 80 + ∠A = 180             (From (1))
⇒2 ∠A = 180 - 80
⇒2 ∠A = 100
⇒∠A = 50

Regards

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sorry
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50° is Angle A
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The theorem used here is Opposite sides are if equal then their opposite angles will also be equal....So here we proved Angle A = Angle C Using Angle sum property Angle A+Angle B+Angle C =180° Angle A+Angle C =100° 2(Angle A)=100°. [PROVED EARLIER] Angle A = 50°
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50 is the measure of Angle A
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Angle A= 50.
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angle a =500
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Thanq very much
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