Because the distance between the corresponding point and the rotation center is always the same in the two figures before and after rotation, the corresponding points must be on a set of concentric circles with the rotation center as the center and the distance from the corresponding point as the radius, and the angles formed by the connecting line between the corresponding points and the rotation center are equal.
(A) in the square "half angle (45 degrees) model"
(2) The more general "half-angle model" in quadrilateral.
(3) the "half angle (45 degrees) model" in the isosceles right triangle.
(d) Diagonal complementary model (1): "* * isosceles hypotenuse right triangle+right triangle" model (equilateral type)
(d) Diagonal complementary model (2): "* * hypotenuse isosceles right triangle+right triangle" model (ipsilateral type)
(d) Diagonal complementary model (3): "equilateral triangle pair 120* model"
(4) Diagonal complementary model (4): "120 isosceles triangle to 60 model"
(5) Other models (1): "equilateral triangle to 30 models"
(5) Other models (2): "isosceles right triangle embedded in 45-degree model" (front embedding)
(5) Other models (3): "The isosceles right triangle is included in the 135 degree model"
(5) Other models (4): "120 isosceles triangle embedded in 60-degree model"
(5) Other models (5): "120 isosceles triangle with 60-degree model"