Dodecagon dissection
The figure is a regular dodecagon, this animation shows that the orange and pink areas are equal.[br]Just move the slider alpha from 0° to 360°.
Inspired by Tim Brzezinski's Tweet
As Steve Phelps wrote:
The hypotenuse of the right triangle is a diameter of the dodecagon, dividing the dodecagon in half by area. Therefore, the two designated regions are equal in area if the negative spaces in each half of the dodecagon are equal in area.[br]I shall show that the orange and pink areas are equal.