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 \(\perp\) PT
In the right \(\triangle OTP,\) we have:
∴ The length of the radius is 7cm.