Mistakes made by cut-the-knot isoperimeter Isoperimetric Theorem and Inequality cut-the-knot adjusts the shapes in his own way, that is adjust the one point of perimeter that is not pointing to the tip of right angle, but there is still other ways which adjust the whole perimeter to make the shape larger in area, Then he had circular for example, he can not adjust, it maybe the largest in his way, but in other ways it maybe even larger than circular (he needs do more proof in his proof).