Question

O is the centre of the given circle. Which of the lines OA, OB, OC, OD, BD and BA are radii (Plural of radius) and why?

Answer 1

A radius is a line that connects the centre and any point on the boundary of the circle.


From the drawing it can be seen that only OA, OB and OC connect the centre O to a point on the circle boundary.
So, OA, OB and OC are radii of the given circle.
AB, BD and OD are not radii.