Mathematics for IGCSE & O level - Circle Theorems (Section 2 - No. 45)
Given a circle, what is the relationship between an angle formed by two tangents at the external point and the angle formed at the centre by the radius that meets the tangent?
They are equal.
They are supplementary.
They are complementary.
There is no relationship.
Explication
The angle formed by two tangents and the radii at the point of contact are complementary because the radii are perpendicular to the tangents.