Coordinate Geometry IGCSE
Coordinate Geometry Gradient (Slope) of a Straight Line The gradient of a straight line is defined as the ratio of the vertical change to the horizontal change between two points on the line. For two points A(x₁, y₁) and B(x₂, y₂) on a line, the gradient is calculated as: gradient of AB = (y₂ - y1) / (x₂ - x1) Length of a Line Segment The length of a line segment PQ between two points (x₁, y₁) and (x₂, y₂) is given by: PQ = √[(x₂ - x1)² + (y₂ - y1)²] Equations of Straight Lines Form Data Required Equation Slope-point form Slope m, one point (x₁, y₁) y - y₁ = m(x - x₁) Two-point form Two points (x₁, y₁) and (x₂, y₂) (y - y₁) / (y2 - y1) = (x - x₁) / (x2 - x1) Slope-intercept form Slope m, y-intercept c y = mx + c Two-intercept form x-intercept a, y-intercept b x/a + y/b = 1 Special Cases Horizontal Line: Parallel to x-axis, equation: y = c (constant) Vertical Line: Parallel to y-axis, equation: x = a (constant) Note: The gradient of a horizont