Here's a brain teaser to play with. Take a look at the attached image, and tell me - what is the radius of the circle? The two crossed lines are diameters that cross at the center of the circle.

Hint: if you find yourself thinking of sines or cosines of angles there's an easier way.

ebaines, just glancing at it, is it
r=8?

Is it that easy?

Hello Galactus - that was quick - very good! Yep, it's that easy. Just consider the diagonal of that rectangle - it's 8 as measured from lower left to upper right (as in the original pic) or from upper left to lower right. The 4 was thrown in just to make it look more complicated than it really is. Like this:

Yep, that's exactly what I seen. I thought perhaps I was flubbing up.

I will post one I ran across recently. Fun little problem.