User:Tohline/Math/EQ PminusHalf01

	<math>~P_{-1 / 2}(z)</math>	<math>~=</math>	<math>~ \frac{2}{\pi} \biggl[\frac{2}{z+1}\biggr]^{1 / 2} ~K\biggl( \sqrt{ \frac{z-1}{z+1}} \biggr) </math>	… for example …		<math>~P_{-1 / 2}(\cosh\eta)</math>	<math>~=</math>	<math>~ \biggl[ \frac{\pi}{2} ~ \cosh \frac{\eta}{2} \biggr]^{-1} K\biggl( \tanh \frac{\eta}{2} \biggr) </math>
Abramowitz & Stegun (1995), p. 334, eq. (8.13.1)					Abramowitz & Stegun (1995), p. 334, eq. (8.13.2)