(a, f)
return -geometric_conj_ab(a, -f)
Conjugation relation for geometrical beams under paraxial conditions.

    Takes the object distance (for geometric_conj_af) or the image distance
    (for geometric_conj_bf) to the optical element and the focal distance.
    Then it returns the other distance needed for conjugation.

    See Also
    ========

    geometric_conj_ab

    Examples
    ========

    >>> from sympy.physics.gaussopt import geometric_conj_af, geometric_conj_bf
    >>> from sympy import symbols
    >>> a, b, f = symbols('a b f')
    >>> geometric_conj_af(a, f)
    a*f/(a - f)
    >>> geometric_conj_bf(b, f)
    b*f/(b - f)
Conjugation relation for geometrical beams under paraxial conditions.
Conjugation relation for geometrical beams under paraxial conditions .
def geometric_conj_af(a, f):
    """
    Conjugation relation for geometrical beams under paraxial conditions.

    Takes the object distance (for geometric_conj_af) or the image distance
    (for geometric_conj_bf) to the optical element and the focal distance.
    Then it returns the other distance needed for conjugation.

    See Also
    ========

    geometric_conj_ab

    Examples
    ========

    >>> from sympy.physics.gaussopt import geometric_conj_af, geometric_conj_bf
    >>> from sympy import symbols
    >>> a, b, f = symbols('a b f')
    >>> geometric_conj_af(a, f)
    a*f/(a - f)
    >>> geometric_conj_bf(b, f)
    b*f/(b - f)
    """
    a, f = map(sympify, (a, f))
    return -geometric_conj_ab(a, -f)
def geometric_conj_af ( a , f ) : a , f = map ( sympify , ( a , f ) ) return - geometric_conj_ab ( a , - f )