Hello, BG5965!

Let , radius2) In the figure, O is the centre of the circle.

A and B are two points on the circle so that triangle OAB is an equilateral triangle.

OA is produced to C so that OA = AC.

Find the angle ABC and prove whether CB is tangent to the circle at B.

. . Then: .

In

Then: .

Hence: . and is tangent to the circle.

Since , then