Question

The angle between two radii OA and OB is a straight angle then AB is called ____.

• A. diameter
• B. chord
• C. radius
• D. circumference

Answer 1

The correct option is A

diameter

In the above figure, OA and OB are two radii of the circle with centre O. The angle between OA and OB is less than ${180}^{\circ }$. Rotate OB anti clockwise such that OA and OB will be at ${180}^{\circ }$, then we will get a diagram as shown.

Clearly, AB is a chord passing through the centre which makes it the longest chord i.e., diameter.