## Lines and points

The equation of a straight line is given by:

where a is the slope of the line. If a = 0, the line is horizontal. b indicate the intersection of the line with the y-axis.

## Finding the equation of a line, when two points are given

The equation of a straight line, two points are given

It’s possible to find the equation of a straight line, when two of its points are given:

(x1,y1) and (x2, y2).

First you have to determine a and b of the equation of a straight line:

a and b can then be substituted into the equation of a straight line.

## The equation of a straight line when two points are given

 Point 1 x1: y1: Point 2 x2: y2:

## Finding the equation of a line, when a point and the line’s slope is given

The equation of a straight line passing through the point (x0, y0) and with the slope a is given by:

If the angle θ between the x-axis and the line is given instead of the slope a, it’s possible to calculate a in the following way: