In∆ABC ,BC=AB and $\angle$B=80 then $\angle$A is equal to
a)80
b)40
c)-50d)-100

Given: 
 In triangle ABC,  AB = BC,  $\angle$ B = 80°

To find:  Find the $\angle$ A

Solution:

So, it is an isosceles triangle.

so the angles A and C are equal. $\angle$ A = $\angle$ C

$\angle$ A + $\angle$B + $\angle$ C = 180

80 + $\angle$ A +$\angle$ C = 180

$\angle$ A + $\angle$ C = 180 - 80

$\angle$ A + $\angle$ C = 100

$\angle$ A + $\angle$ B = 100

2 $\angle$A  =  100

$\angle$A  =  $\frac{100}{2}$

$\angle$ A = 50

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Updated on: 10-Oct-2022

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