The two straight lines are parallel, with the same internal dislocation angle and the same position angle: the corresponding angles of congruent triangles and similar triangles are equal; The antipodal angle is equal; The outer angle of a triangle is equal to the sum of two non-adjacent inner angles; The complementary angles of the same angle or equal angle are equal: the complementary angles of the same angle or equal angle are equal: the diagonal lines of the parallelogram are equal.

In geometry, an angle is a geometric object composed of two rays with a common endpoint. These two rays are called the edges of an angle, and their common endpoint is called the vertex of the angle. The general angle is assumed to be in Euclidean plane, but it can also be defined in Euclidean geometry. Angles are widely used in geometry and trigonometry.

Euclid, the father of geometry, once defined the angle as the relative inclination of two non-parallel straight lines in the first plane. Proclos thinks that angle may be a trait, a quantifiable quantity, or a relationship. Oldham thinks that an angle is a deviation from a straight line, and Cabus of Antioch thinks that an angle is a space between two intersecting straight lines. Euclid thought that an angle was a relationship, but his definitions of right angle, acute angle or obtuse angle were all broken by the measurers.

Advantages of mathematics

1, to meet the needs of people's daily life, work, counting, calculation and reasoning. In people's daily life and work, it is essential to count things, calculate various quantities and compare related quantities. Mathematical knowledge and thinking methods are needed here.

2. Exercise the thinking level and quality of several holes, such as calculating ability, logical thinking and spatial imagination. Mathematical science is a rigorous and meticulous science, so people's thinking has been exercised while learning mathematical science knowledge.

3. Mathematics learning can provide necessary technical support for further study of natural science and social science. Mathematics, as a basic subject to understand the world, can support the in-depth development of different applied sciences ideologically and technically like a computer system.