1, let F 1 and F2 be the two focuses of ellipse C, and P is any point on C. If straight line AB intersects ellipse C at point P and A and B are located on both sides of straight line P, then ∠APF 1=∠BPF2.

2. Let F 1 and F2 be the two focal points of ellipse C, and P be any point on C. If the straight line AB is the normal of C at point P, then AB divides F1PF2 equally.

3. In the plane rectangular coordinate system, high school textbooks describe ellipses with equations. The "standard" in the elliptic standard equation means that the center of the circle is at the origin and the axis of symmetry is the coordinate axis.

4. when the focus is on the y axis, the standard equation is: y 2/a 2+x 2/b 2 =1(a > b > 0), where a>0 and b>0. The larger one of A and B is the long semi-axis length of the ellipse, and the shorter one is the short semi-axis length (the ellipse has two symmetrical axes, which are cut by the ellipse and have two line segments.

brief introduction

An ellipse is a closed cone section: a plane curve intersects a plane through a cone. Ellipse has many similarities with the other two forms of conical section: parabola and hyperbola, which are both open and unbounded. The cross section of a cylinder is elliptical unless it is parallel to the axis of the cylinder.

An ellipse can also be defined as a set of points, so that the ratio of the distance between each point on the curve and a given point (called focus) to the distance between the same point on the curve (called directrix) is a constant. This ratio is called eccentricity of ellipse.