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**Coordinate Geometry**

- The equation of a straight line can be written as y = mx + c, where m is the gradient and c is the intercept with the vertical axis.
- The
**gradient**of a line passing through the points (x1,y1) and (x2,y2) is (y2 -y1) / (x2 -x1). - The equation of the straight line with gradient m that passes through the point (x1, y1) is y-y1 =m(x-x1).
- Lines are
**parallel**if they have the same gradient. - Two lines are
**perpendicular**if the product of their gradients is -1. - If the gradient of a line is m, then the gradient of a perpendicular line is - 1/m.
- The midpoint of the line joining the points (x1, y1) and (x2, y2) is ((x1+x2)/2,(y1+y2)/2).

- The distance between the points with coordinates (x1,y1) and (x2,y2) is √(x2 -x1)^2 + (y2 -y1)^2.
- The equation of a
**circle**centre (a, b) with radius r is (x-a)^2 +(y-b)^2 =r^2 .

When it comes to AS/A-level Maths, do you know how to find the point of intersection of lines?

That's the end of the topic!

Drafted by Bonnie (Mathematics)