Steps of construction:
(i) Draw a line 'l ' and take point X on it.
(ii) With X as centre and a convenient radius, draw an arc intersecting the line 'l ' at two points A and B.
(iii) With A and B as centres and a radius greater than XA, draw two arcs, which cut each other at C.
(iv) Join AC and produce it to Y. Then XY is perpendicular to 'l '.
(v) With D as centre and a convenient radius, draw an arc intersecting XY at two points C and D.
(vi) With C and D as centres and radius greater than YD, draw two arcs which cut each other at F.
(vii) Join YF, then YF is perpendicular to XY at Y.
