The parametric equation of ellipse x=acosθ, y=bsinθa is the long semi-axis length b, and the short semi-axis length θ is the parameter.
The parametric equation of hyperbola x=asecθ (secant,) y=btanθa is the real semi-axis length b, and the imaginary semi-axis length θ is the parameter.
The parametric equation of parabola x=2pt2, y=2ptp indicates that the distance t from the focus to the directrix is a parameter.
The parametric equation of a straight line x=x'+tcosa, y=y'+tsina, x', y' and a represents a straight line passing through (x', y'), with an inclination angle of a and a parameter of t.
The polar coordinate parameter equation of the curve: p =f(t), θ=g(t).
Coordinate system definition:
1. Plane rectangular coordinate system: two number axes perpendicular to each other on the same plane and having a common origin form a plane rectangular coordinate system, which is called rectangular coordinate system for short.
2. Spatial Cartesian coordinate system: draw three mutually perpendicular number axes with the same unit length from a certain point in space: X axis, Y axis and Z axis, thus establishing the spatial Cartesian coordinate system Oxyz.
Definition of polar coordinates: take a fixed point o on the plane and call it a pole; A ray Ox drawn from the pole o is called the polar axis; Then choose a length unit, an angle unit (usually radian) and its positive direction (usually counterclockwise), thus establishing a polar coordinate system.