Use the formula: Area = 1/2 × base × height
Measure the base of the triangle
Measure the perpendicular height from the base to the opposite vertex
Multiply base by height
Divide the result by 2
Use the formula: Area = √[s(s – a)(s – b)(s – c)] for three known sides
Calculate s = (a + b + c) / 2
Substitute a, b, c, and s into the formula
Use the formula: Area = 1/2 × a × b × sin(C) for two sides and the included angle
Substitute the two side lengths and the angle into the formula