Isosceles Triangle

Isosceles Triangle

How to solve isosceles triangle problems: property, examples, and their solutions.

Property

An isosceles triangle has two congruent sides (legs) and two congruent angles.

An isosceles triangle has
two congruent sides (legs)
and two congruent angles.

Leg: two congruent sides
Base: side that is adjacent to the congruent angles

Example 1

Find the value of x. congruent angles: 3x + 25, 55

The given triangle is an isosceles triangle.

So the given angles are congruent.

So 3x + 25 = 55.

Example 2

Find the value of x. The left isosceles triangle's measure of congruent angle is x. And the right isosceles triangle's measure of congruent angle is 70.

The right triangle is an isosceles triangle.

So the measure of the left blue angle is 70.

The left blue angle is
the exterior angle of the left isosceles triangle.

So x + x = 70.