A straight line is the simplest geometrical curve. Every straight line is associated with an equation. To determine the equation of a straight line, two conditions are required.
y = mx+ c
where m is the slope of the straight line and c is the y intercept.
y − y1 = m(x − x1)
where m is the slope and (x1, y1) is the given point.
where (x1, y1) and (x2, y2) are the two given points.
where a and b are x and y intercepts respectively.
Equation of a straight line in terms of the length of the perpendicular p from the origin to the line and the angle α which the perpendicular makes with x-axis.
x cos α + y sin α = p
The equation ax + by + c = 0 always represents a straight line.