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

Given : BC = AB

$\Rightarrow $$\angle $A = $\angle $C ................ (1) (Angle opposite to equal sides are equal)

Now,

$\Rightarrow $$\angle $A + $\angle $B + $\angle $C = 180 (Angle Sum property)

$\Rightarrow $$\angle $A + 80 + $\angle $A = 180 (From (1))

$\Rightarrow $2 $\angle $A = 180 - 80

$\Rightarrow $2 $\angle $A = 100

$\Rightarrow $$\angle $A = 50

Regards

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