Let’s take an example
Given a line
with point P not on it
With P as center, and any radius,
draw an arc intersecting the line at points A and B
Now with A as center, and
draw an arc.
With B as center, and same radius as before, draw an arc
- Mark the point of intersection of the two arcs as point Q
Join P & Q.
∴ PQ is the line perpendicular to line l