Question

An exterior angle of a triangle is 120 degree and one of the interior opposite angles is 20 degree. Find the other two angles of the triangle.

Answer 1

Hi there !!

We know that :

Exterior angle of a triangle = sum of the 2 interior opposite angles

Here in this case :

Exterior angle = 120°

Also , we are given one of the opposite interior angles as 20°

Let the unknown other interior opposite angle be x

x + 20° = 120°

x = 120 - 20 = 100°

So ,we get the interior opposite angles as 20° and 100°

=========================

We know that

sum of all angles of a triangle = 180°

Let the third unknown angle be y

y° + 20° + 100° = 180°

y° = 180 - 120
= 60°


So the angles of the Δ are :
60° , 100 ° , 20°