Steps of construction:
1. Draw concentric circle of radius 4 cm and 6 cm having same centre .
2. Locate a point P on the circle whose radius is 6 cm.
3.Join the points O and P through lines such that it becomes OP.
4. Draw the perpendicular bisector to the line OP
5. Let O' be the mid-point of PO.
6. Draw arc with centre M as on the small circle on R and Q
7. Join PQ and PR.
10. PQ and PR are the required tangents.