In a plane, a closed curve formed by rotating around a point for a certain length is called a circle.
A triangle is a closed figure composed of three line segments in the same plane but not on the same straight line. It has applications in mathematics and architecture.
A rectangle, also called a rectangle, is a plane figure and a parallelogram with right angles. A rectangle is also defined as a parallelogram stool with four corners at right angles. A square is a special rectangle with four sides of the same length.
Geometry:
Geometry is the study of spatial structure and properties. It is one of the most basic research contents in mathematics, which has the same important position as analysis and algebra, and has a very close relationship. Geometry has a long history and rich contents. It is closely related to algebra, analysis and number theory. Geometric thought is the most important thought in mathematics. The temporary development of each branch of mathematics tends to geometry, that is, to explore various mathematical theories with geometric viewpoints and thinking methods.
The word geometry comes from the Greek word "γ ε ω μ ε ρ? Alpha ",by" γ? Jujube Jue α "(ground) and" μ ε ρ ε? ν "(measurement) is a combination of two words, which refers to the measurement of land, that is, geodesy. Later it was translated into Latin "geometria". The Chinese word "geometry" was coined by Xu Guangqi when Matteo Ricci and Xu Guangqi jointly translated The Elements of Geometry in the Ming Dynasty.