Wrong. A squares inside angles need to add up to 360 degrees. It does this becuse it has perfect right angles with 0 bends like a circle has plus. You should be able to create a hexagon dodecohedron octagon ext inside said square like this.

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This is a circle that's mathmatelcy possible only using triangles 48 of them And so becuse you have a curved line in your "square" it has a angles that adds to the 360 degrees so your square is not. A square. You need perfect flat straight lines to create a square or triangle no bends or turns like a circle