To construct a line perpendicular to line AB and passing through an external point M.
Step 1:- Keep point A as center and draw a circle using compass opened with a width equal to radius AM.
Step 2:- Similarly, Keep point B as center and draw another circle using compass opened with a width equal to radius BM.
Step 3:- The two circles drawn so far would cut at two points, first point is M and second point is N.
Step 4:- Join the two points M and N using straightedge.
Step 5:- Therefore, we have a line MN that is perpendicular to line AB.