The distance formula
The length of a line segment between two points P₁(x₁, y₁) and P₂(x₂, y₂) is found using the distance formula, derived from the Pythagorean theorem.
Formula: d = √((x₂ - x₁)² + (y₂ - y₁)²)
For example, the distance between (1, 2) and (4, 6) is √(3² + 4²) = √25 = 5.