Use ruler and compasses only for answering this question. Draw a circle of radius 4 cm. Mark the centre as O. Mark a point P outside the circle at a distance of 7 cm from the centre. Construct two tangents to the circle from the external point P. Measure and write down the length of any one tangent.

Steps of construction :

1. Construct a circle with centre as O and radius = 4 cm.

2. Mark a point P at a distance of 7 cm from the centre. Join OP. Draw its perpendicular bisector to meet OP at M.

3. With M as centre and OM (or MP) as radius, draw a circle. Let this circle intersect the given circle with centre as O at points A and B.

4. Join PA and PB.

On measuring, PA = PB = 5.7 cm

Hence, the length of each tangent = 5.7 cm.