Let's look at the geometric characteristics of a isosceles triangle. But first please review the definition of Perimeter Of Two-Dimensional Shapes, Angle and Right Angle.

- An isosceles triangle has two unique features.
- The first unique feature is two sides have exactly the same length: sides A.
- The second unique feature
the angles at the base of the triangle are exactly the same. In other words
**∠BA**and**∠AB**are equal. The sum of the interior angles is 180°. - Special note, all sides of an isosceles triangle must be greater than zero.

**Perimeter Of An Isosceles Triangle Formula**

Formula = Side A + Side A + Side B =

Formula = 2 A + B =

Formula = (2 × A) + B