A is the length of the semi-major axis, that is, the distance from the origin to the far vertex.

b？ Is the semi-minor axis length, that is, the distance from the origin to the nearest vertex.

An ellipse is the trajectory of a moving point P. The sum of the distances from the moving point P to the fixed points F 1 and F2 in a plane is equal to a constant (greater than |F 1F2|), and F1and F2 are called the two focuses of the ellipse. The mathematical expression is | pf1|+pf2 | = 2a (2a > | f1F2 |).

The standard equation of ellipse * * * is divided into two cases:

When the focus is on the X axis, the standard equation of the ellipse is: X 2/A 2+Y 2/B 2 =1,(a>b>0);

When the focus is on the Y axis, the standard equation of the ellipse is: Y 2/A 2+X 2/B 2 =1,(a>b>0);

Where a 2-c 2 = b 2, it is deduced as: pf1+pf2 >; F 1F2(P is the point f on the ellipse as the focus).