A diagonal line connecting four points, assuming that the intersection point of this diagonal line is O, connects four line segments OA, OB, OC and OD (where O is the intersection point and A, B, C and D are four points), and proves that AO=CO and BO=DO, that is, it is proved that the rectangle ABCD (that is, the quadrilateral obtained by connecting diagonal lines) is an orthogonal rectangle through geometric reasoning. Because the diagonal of the rectangle is equally divided, we can get OA=OC=OB=OD, which is a four-point * * * circle. Prove it.

1. oblique

Diagonal angle refers to the internal angle sandwiched between two sides in a triangle, which is called the diagonal of the third side. Equilateral and isometric: In an isosceles triangle, the diagonal angles of two isosceles are also equal. Equiangular equilateral: If two internal angles in a triangle are equal, their opposite sides are also equal, so it can be judged whether it is an isosceles triangle according to whether the internal angles of the triangle are equal.

Step 2 supplement

The definition of complementarity can be further extended to other fields in mathematics, such as function and geometry. In a function, complementarity can be defined as the sum of two functions equals a constant. For example, the sum of two sine functions can be constant, where the frequencies and amplitudes of the two functions are different. In geometry, complementarity can be defined as the sum of two graphs equals to a complete graph. For example, the sum of two triangles is equal to a quadrilateral, where the two triangles are different in shape and size.

The definition of complementarity can also be applied to practical problems. For example, in physics, complementarity is often used to describe the interaction of particles. In economics, complementarity is often used to describe the interdependence between commodities.

When applying the supplementary definition, we need to pay attention to some details and precautions. First of all, the definition of complementarity requires that the sum of two quantities must be equal to a constant. If this condition is not met, then these two quantities are not complementary. Secondly, the definition of complementarity can be different in different fields. For example, in geometry, the definition of complementarity may be different from that in function. Therefore, when using supplementary definitions, it is necessary to ensure that the correct definition is used.