Drawing perpendicular to a line through a point – Using ruler and compass

Let’s take an example

1. Given a line l
   with point P marked on it

2. With P as center, and any radius,
   draw an arc intersecting the line at points A and B
   
   
   
   3. Now with A as center, and radius more than AP,

           draw an arc.

           With B as center, and same radius as before, draw an arc

   
   
   4.Mark the point of intersection of the two arcs as point Q Join P & Q.
   
   

   
   ∴ PQ is the line perpendicular to line l