An Etymological Dictionary of Astronomy and Astrophysics

If f(x) and φ(x) are two → continuous functions on the → interval [a,b] and → differentiable within it, and φ’(x) does not vanish anywhere inside the interval, there will be found, in [a,b], some point x = c, such that [f(b) - f(a)] / [φ(b) - φ(a)] = f’(c) / φ’(c).

See also: → Cauchy’s equation; → theorem.