Bifocal frame of reference

One calls bifocal frame of reference compared to two points A1 (0,0, a) and A2 (0,0, - A), a system where the current point P is located by its Azimut, and its distance A1P and A2P.

The practice is to pose:

U = + A2P /2a and v = A1P - A2P /2a.

Application

In mechanics, it is very much used as soon as it potential-of-force is of the type: $U\; (r\_\; 1,\; r\; \_2)\; =\; \backslash \; frac\; \{1\}\; \{r\_\; 1r\; \_2\}\; \backslash \; cdot\; F\; (U)\; +g\; (v)$

In particular problem of the movement of a planet between two fixed stars celebrates it, solved by Euler, uses this type of coordinates.

See too

• Keplerian Movement
• Keplerian Movement, movement of Euler.
• parabolic Frame of reference

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