Question

I know it’s an isosceles but I need reasons why

Answer 1

it is an isosceles triangle.

Explanation:

first of, total angle of a triangle is 180°

angle on a straight line is 90°

if AB'C is 80°

AC'B =40

then A = 60°

which proves the notion that all the sides are unequal which is the basic characteristic of an isosceles triangle.