# Formulas for the Area of a Triangle

**1.** , where is the base and is the altitude of the triangle.

**2.** The area of an equilateral triangle

, where is the length of each side of the triangle.

**3.** The area of a triangle when two adjacent sides and the included angle is given by

4. The area of a triangle when the length of all sides are given

where

**5.** The area of a triangle with vertices is given by the formulas