The area is calculated using the formula A = (base × height) / 2. For example: a triangle with base 10 cm and height 5 cm has area (10 × 5) / 2 = 25 cm².

Use Heron's formula: calculate the semi-perimeter s = (a+b+c)/2, then A = √(s(s-a)(s-b)(s-c)). For example: sides 3, 4, 5 give s=6, A=√(6×3×2×1) = 6 cm².

A right triangle has one angle that is exactly 90 degrees. The sides are called legs (the two shorter sides) and hypotenuse (the longest side opposite the right angle).