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How to calculate the focal length of an ellipse?
The relationship among a, b and c in the elliptic formula is a2 = B2+C2 (a > b >; 0)。

The major axis is 2a, the minor axis is 2b, and the focal length is 2c.

An ellipse is the trajectory of a moving point P, and the sum of the distances between this point and the fixed points F 1 and F2 in a plane is equal to a constant (greater than |F 1F2|). F1and F2 are called the two focuses of the ellipse, and their mathematical expressions are | pF 1 || pf2 |. |F 1F2|).

Brief introduction of ellipse properties

1, range: focusing on X axis, -a≤x≤a, -b≤y≤b, focusing on Y axis, -b≤x≤b,-A ≤ Y ≤ A.

2. Symmetry: symmetry about the X axis, symmetry about the Y axis, and symmetry about the origin center.

3. Vertices: (a, 0), (-a, 0), (0, b), (0, -b).

4. Eccentricity: e=c/a or e = √ (1-b 2/a? )。

5. Centrifugal rate range: 0

6. The smaller the eccentricity, the closer to the circle, the greater the eccentricity and the flatter the ellipse.

7. Focus (when the center is the origin): (-c, 0), (c, 0) or (0, c), (0, -c).