To find the distance between two points (x₁, y₁) and (x₂, y₂), use the distance formula: d = √((x₂ - x₁)² + (y₂ - y₁)²).
This formula comes from the Pythagorean theorem. The horizontal distance (x₂ - x₁) and vertical distance (y₂ - y₁) form the legs of a right triangle. The straight-line distance is the hypotenuse.
If you need the distance from (1, 2) to (4, 6), calculate √((4-1)² + (6-2)²) = √(9 + 16) = √25 = 5.