# Find the perimeter of a triangle

The perimeter is the length of all sides of the polygon. The perimeter is denoted by a capital Latin letter P. There are several ways to find the perimeter of a triangle, which one to use depends on the initially known data.

Find the perimeter knowing three sides

**Side length A**

**Side length B**

**Side length C**

Find the perimeter of a triangle, knowing its area and the radius of the inscribed circle

**Area of a triangle S**

**Inscribed circle radius r**

Find the perimeter of a triangle, knowing the two sides and the angle between them

**Famous side А**

**Famous side B**

**Angle between sides α**