Question

∆ABC is an isosceles triangle with AB =AC, if angle A=100° find the measure of angle B.

Answer 1

angles opposite to equal sides in a triangle are equal
as AB = AC
so angle C = angle B
again, angle A + angle B + angle C = 180 (angle sum property of triangle)
or 100 + angle B + angle B = 180
or 2 angle B = 80
or angle B = 40

Answer 2

AnswEr:

We have ,

AB = AC

→ $\angle$B = $\angle$C

$\qquad\tt{[Angles\:opposite\:to\:equal\:sides\:are\:equal]}$

In ∆ABC, we have

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

→ $\angle$A + $\angle$B + $\angle$B = 180°

→ 100° + 2 $\angle$B = 180°

→ 2 $\angle$B = 80°

→ $\angle$B = 40°

Hence, $\angle$B = $\angle$C = 40°

#BAL

#Answerwithquality