(i) Take any ray OA.
(ii) With O as centre and any convenient radius, draw an arc cutting OA at B.
(iii) With B as centre and the same radius, draw an cutting the first arc at C.
(iv) With C as centre and the same radius, cut off an arc cutting again the first arc at D.
(v) With C and D as centre and radius of more than half of CD, draw two arcs cutting each other at E, join OE.