Coordinate Geometry Key Points
Coordinate Geometry Key Points
Coordinate Geometry Key Points
In coordinate geometry we use graphs and coordinates to find measurements and other
useful information about geometric figures. We will be focusing on coordinate geometry as
it applies to straight lines.
CONCEPTS COVERED:
1. Midpoint of a line segment - this is the POINT that is halfway between two given points.
𝑥! + 𝑥" 𝑦! + 𝑦"
• What is the formula for midpoint? ! , '
2 2
2. Length of a line segment – this is the distance between two endpoints.
• What is the formula for length of a line? ((𝑦" − 𝑦! )" + (𝑥" − 𝑥! )"
3. Gradient of a line – this is a NUMBER that describes the slope of a line (how slanted the line may be)
𝑦" − 𝑦!
What is the formula for gradient? 𝑚=
𝑥" − 𝑥!
What is the gradient of a horizontal line? 𝑚=0
What is the relationship between the gradients of parallel lines? 𝑔𝑟𝑎𝑑𝑖𝑒𝑛𝑡𝑠 𝑎𝑟𝑒 𝑒𝑞𝑢𝑎𝑙
4. Intercepts of a straight line – points on a straight line which intersect the x axis and y axis
What is known about every point that lies on the y-axis? 𝑡ℎ𝑒 𝑥 𝑐𝑜𝑜𝑟𝑑𝑖𝑛𝑎𝑡𝑒 𝑖𝑠 𝑎𝑙𝑤𝑎𝑦𝑠 0
5. Equation of a straight line – an equation which describes the relationship between the coordinates
of points on a given line
What are the two values you need to know to determine the 𝑔𝑟𝑎𝑑𝑖𝑒𝑛𝑡 (𝑚) 𝑎𝑛𝑑
equation of a straight line? 𝑦 − 𝑖𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 (𝑐)