STRAIGHT LINES

 

Gradient (m):

 

Intercept (c): The intercept (c) is where the line cuts the y axis. To find this, let . (NB to find where the line cuts the x axis, let  )

 

Equations: There are three versions of the equation of a straight line.

 

EQUATION

USE WHEN YOU ARE GIVEN

Gradient (m) and intercept (c)

Gradient (m) and 1 point

Two points  and

 

 

Parallel Lines: gradients  and  are equal

 

Perpendicular Lines:        

 

Midpoint of Line:                 

 

Distance between 2 points  and  (use Pythagoras)

 

                     In 2D:        

 

                     In 3D:        

 

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