Legendre Duplication Formula
Gamma functions of argument
can be expressed in terms of gamma functions of smaller arguments. From the definition of the beta function,
 |
(1)
|
Now, let
, then
 |
(2)
|
and
, so
and
Now, use the beta function identity
 |
(7)
|
to write the above as
 |
(8)
|
Solving for
and using
then gives
REFERENCES:
Abramowitz, M. and Stegun, I. A. (Eds.). Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, 9th printing. New York: Dover, p. 256, 1972.
Arfken, G. Mathematical Methods for Physicists, 3rd ed. Orlando, FL: Academic Press, pp. 561-562, 1985.
Erdélyi, A.; Magnus, W.; Oberhettinger, F.; and Tricomi, F. G. Higher Transcendental Functions, Vol. 1. New York: Krieger, p. 5, 1981.
Morse, P. M. and Feshbach, H. Methods of Theoretical Physics, Part I. New York: McGraw-Hill, pp. 424-425, 1953.