Hello, Jammix!

Is there any more information?

I suspect that I know the solution . . . but it's only a guess.

Circumscribe a square about a semicircle.

Square is circumscribed about the (tilted) semicircle.Code:R B * - -.-.*.o.*.-.- * C | .*:::::|:::::*.| | *:::::::|:::::::o S |*::::::::|:::::* | |:::::::::|:::* r | *:::::::::|:* * Q o:-:-:-:-:O - - - o *:::::::* : * |:::::*r : | | ::* : | A * o - - - * - - - * D P E

The circle has center and radius

is an isosceles right triangle.

Hypotenuse

Let , the side of the square.

Then: .

Therefore: .