We have studied combination of algebra and geometry in two-dimensional coordinate geometry. Let us recollect the following Important Formula of Straight Lines in Co-ordinate Geometry, we learnt earlier.

Straight Lines – Important Formula

Slope of a Line

Slope of line passing through 2 given points

P(x_{1},y_{1}) and Q(x_{2}, y_{2}) are two points on non-vertical line l whose inclination is 𝜃 (F-2). So, x_{1}≠x_{2}, (otherwise the line will become perpendicular to x-axis and its slope would be undefined). The inclination of the line l may be acute or obtuse. We would take up take both cases.

Draw perpendicular QR to x-axis and PM perpendicular to RQ.