Construct a tangent to a circle of radius 4cm from a point on the concentric circle of radius 6cm.

Steps of construction:Draw two concentric circles with radii 4cm and 6cm.Draw the radius OP of the bigger circle.Make a perpendicular bisector of OP which intersects OP at point O'.Taking O'P as radius, draw another circle.From point P, draw tangents PQ and PR; as shown in the figure