1. With centre O and radius = 3cm, draw a circle.
2. Take any point P outside the circle.
3. Through the external point P draw a straight line PBA meeting the circle at A and B.
4. Draw a semi-circle on AP as diameter.
5.Draw BC ⊥ AP, which intersects the semi-circle at C.
6. With centre P and radius PC draw an arc cutting the circle at Q.
7. Join PQ. Then PQ is the required tangent.