Let's draw a circle with a certain radius. We inscribe a triangle with one side being the diameter of the circle.  The opposite angle will be 90 degrees according to Thales (semi circle theorem).[br][br]Now divide the diameter by the Sine of it's opposite (90 degree) angle. What number do you get?[br]Also divide the other side lengths by the sine of their opposite angle. What's the answer? [br][br]Will this also work for triangles that are not on the diameter of the circle?[br][br]Hint: Sin(90) = 1 i.e. the sine of 90 degrees is 1.