Coordinate Geometry

Straight line graphs

The distance between two points can be calculated by constructing a right-angled triangle between the coordinates and applying Pythagoras’ Theorem:

The coordinate of the midpoint of the line between the points (????1, ????1) and (????2, ????2) is given by:

If C divides the line AB in the ratio p : q where A(????1, ????1) and B(????2, ????2):

The gradient of the line between the points (????1, ????1) and (????2, ????2) is given by:

Given the gradient, ????, and a single point, (????1, ????1), the equation of a line can be generated using:

or

If the lines with the gradients m1 and m2 are parallel:

The perpendicular bisector of the line AB is a straight line that is

  • Perpendicular to line AB
  • Passes through the midpoint of line AB

If the gradient of AB is m then the gradient of its perpendicular bisector is:

Equation of circle

 

The tangent to the circle is perpendicular to the radius of the circle at the intersection point.

The perpendicular bisector to a chord of the circle will pass through the centre C.