Re: Simplifying Bessel Functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg92505] Re: Simplifying Bessel Functions*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Thu, 2 Oct 2008 04:34:36 -0400 (EDT)*Organization*: The Open University, Milton Keynes, UK*References*: <gbvlu6$bch$1@smc.vnet.net>

Aaron Fude wrote: > What do I need to do to make mathematica recognize the following > expression as zero: > > BesselJ[0, BesselJZero[0, n]] You could add an up-value to BesselJZero. Below, we unprotect the built-in symbol BesselJZero and add the new rule thanks to *TagSetDelayed* (shortcut "/: :=", w/o the quotes). In[1]:= BesselJ[0, BesselJZero[0, n]] Unprotect[BesselJZero]; BesselJZero /: BesselJ[0, BesselJZero[0, n_]] := 0 Protect[BesselJZero]; BesselJ[0, BesselJZero[0, n]] Out[1]= BesselJ[0, BesselJZero[0, n]] Out[5]= 0 (Note that the above definition is very broad since it works for any n, not just for positive integers.) HTH, -- Jean-Marc