Draw a circle and let P be a point such that OP = 25cm.
Let TP be the tangent, so that TP = 24cm
Join OT where OT is radius.
Now, tangent drawn from an external point is perpendicular to the radius at
the point of contact.
∴ OT⊥PT
In the right △ OTP, we have:
∴ The length of the radius is 7 cm.