Question

ABC is a triangle .if AB=AC and angle BAC =80°,then find angle ABC

Answer 1

here
triangle ABC
AB=AC
therefore
B=C=x
A=80°

measure of triangle is 180°
A+B+C=180
80+x+x=180
2x=180-80
2x=100
x=100/2
x=50

therefore
angle ABC=50°

Answer 2

Given :

$AB=AC\\\\\angle BAC=80^\circ$

To find : $\angle ABC=?$

Solution :

In ΔABC, it is an isosceles triangle,

So, ∠ ABC = ∠ACB = x

According to the sum of angles of triangle :

$\angle A+\angle B+\angle C=180^\circ\\\\80^\circ+x+x=180^\circ\\\\2x=180-80\\\\2x=100\\\\x=\dfrac{100}{2}\\\\x=50^\circ$

Hence, the measure of $\angle ABC=50^\circ$.