Use the formula: Area = 1/2 × base × height
Measure the base of the triangle
Measure the perpendicular height to that base
Multiply base by height
Divide the result by 2
If you know all three sides, use Heron’s formula: Area = √[s(s-a)(s-b)(s-c)]
In Heron’s formula, s = (a + b + c) / 2
If you know two sides and the included angle, use: Area = 1/2 × a × b × sin(C)