Distance between two parallel lines

Distance Between Two Parallel Lines

Perpendicular distance between the lines ax + by + c = 0 (1)

and ax + by + d = 0 is (2)

Two Straight Lines Equally Inclined To A Straight Line

If two straight lines with slope m₁ and m₂ are equally inclined to a straight line of slope m then

= .

Equation of Straight Lines through (h, k) making an angle α with the line

y = mx + c are

y − k = tan(θ − α) (x −h) and

y − k = tan(θ + α) (x −h) where tanθ = m.