A circle, radius two units, center the origin , cuts the x-axis at A and B and cuts the positive y-axis at C. Prove that AB subtends a right angle at C.

I have tried drawing it so i can understand the problem better in order to answer the question. but looking at the sketch. It creates an isosceles

triangle not a right angle

I have tried a different sketch;

the problem with this sketch is that c is not the positive y-axis.

any tips so i can figure it out

thanks