Fix two nails at the focus of the ellipse, and tie a rope to the nails. The length of the rope depends on the size of the ellipse you need. You can try it while drawing, and use a pencil to straighten the rope. Rotate around the two nails to draw an ellipse.
1.
Mathematical pole drawing method
2.
Software drawing method
Window,
CoreDraw,
Pro-E,
SolidWork...
3.
Curve board assistance
4.
Generally, four-centered arcs are used to express the approximate shape of an ellipse
5.
Jacobi
Elliptic function expansion method
6.
Affine method
(The affine correspondence, that is, the affine property, can be used to find out whether a circle is in any plane projection)