Construct a tangent to a circle of radius 4 cm from a point on the concentric circle of radius 6 cm and measure its length. Also verify the measurement by actual calculation.

AcademicMathematicsNCERTClass 10


Radii of two co-centric circles.

To do: 

We have to construct a tangent of the circle with radius 4 cm from a point on the co-centric circle of radius 6 cm.


Steps of construction:

1. Draw two concentric circle with centre O and radii 4 cm and 6 cm Take a point P on the outer circle and then join OP 

2. Draw the perpendicular bisector of OP. Let the bisector intersects OP at M 

3. With M as the center and OM as the radius, draw a circle. Let it intersect the inner circle at A and B.

4. Join PA and PB. 

Therefore, PA and PB are the required tangents. 

In $\triangle OAP$,





$OA=2\sqrt5\ cm$


$OB=2\sqrt5\ cm$

Updated on 10-Oct-2022 13:23:52