double arspmfm(double g, double m);
Computes the Prandtl-Meyer angle 
from the given mach number 
.
| Argument | Intent | Description |
| g | in | Specific heat constant |
| m | in | Mach number |
Return value
This function returns the Prandtl-Meyer angle 
for the given mach number 
or NAN (Not-a-Number) if an error has
occurred).
. 
.