Ellipse, hyperbola and parabola in analytic geometry are widely used in production or life. For example, the reflector of the spotlight bulb of a movie projector is an ellipse, the filament is in one focus and the film door is in another focus. Searchlights, spotlights, solar cookers, radar antennas, satellite antennas and radio telescopes are all made by using the principle of parabola. Therefore, the establishment of analytic geometry can be said to be a very important event in the history of mathematics, because analytic geometry introduced a series of new mathematical concepts and promoted the development of mathematics, such as introducing variables into mathematics, which made mathematics enter a new development period, which is called variable mathematics period. Engels once commented on analytic geometry: the turning point in mathematics is Descartes' variable, and with the change of books, movement enters mathematics; With variables, dialectics enters mathematics; With variables, differentiation and integration are immediately needed. So what exactly is analytic geometry? Simply put, it is to first establish a coordinate system and determine two mutually perpendicular straight lines with a certain direction and measurement unit, which is called a rectangular coordinate system on the plane. Then the coordinate system can be used to establish a one-to-one correspondence between points on the plane and a pair of real numbers x and y. In addition to rectangular coordinate system, there are oblique coordinate system, polar coordinate system, spatial rectangular coordinate system and so on. There are spherical coordinates and cylindrical coordinates in the spatial coordinate system.