The length of the tangent from an external point A on a circle with centre O is
A. always greater than OA
B. equal to OA
C. always less than OA
D. cannot be estimated
Answer:C
The length of the tangent from an external point A on a circle with centre O is
A. always greater than OA B. equal to OA C. always less than OA D. cannot be estimated
Explanation: Since the tangent is perpendicular to the radius of the circle, then the angle between them is 90º. Thus, OA is the hypotenuse for the right triangle OAB, which is right-angled at B. As we know, for any right triangle, the hypotenuse is the longest side. Therefore the length of the tangent from an external point is always less than the OA.