two questions, on the same vein...

the radius of the red circle is given, and its center point is always at 0,0.

point A moves, tracing the path of the red circle.

given point A, how would you calculate the remaining point coordinates to form the largest possiblewithin the red circle?square

given point A, how would you calculate the remaining point coordinates to form the largest possiblewithin the red circle?equilateral triangle

thanks!