Given a Rectangle (x:0,y:0, width:W, height:H) and an angle to rotate it
what is the minimum resulting rectangle required to to encapsulate the result?
where the CENTER remains constant (ie. I want to rotate a rectangle around its center point, with no clipping)
NOTE : rectangle… which may or may not be square

If I understood well (probably I didn’t :() you need a square centred in the same centre of the original rectangle, which side is the diagonal of the rectangle side = sqrt(W^2+H^2)