Step of construction:
1. Draw a circle with centre O and radius 3 cm
2. Produce the diameter of the circle to both the ends up to P and Q such that OP = OQ = 7cm
3. Draw the perpendicular bisector of the line PO and QO and mark the midpoint as M and M' respectively
4. Draw arc with centre M on circle on R and S
5. Draw arc with centre M' on circle on T and U
6. PR , PS , QT and QU are the required tangents.