Re: Getting rid of ProductLog

*To*: mathgroup at smc.vnet.net*Subject*: [mg49258] Re: Getting rid of ProductLog*From*: Bill Rowe <readnewsciv at earthlink.net>*Date*: Fri, 9 Jul 2004 02:26:37 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

On 7/8/04 at 2:51 AM, robert.hulme at gmail.com (Robert Hulme) wrote: >Solve[a^b - b == c, b] >Which gives me: >Out[3]//TextForm= > Log[a] > ProductLog[-(------)] > c > a >{{b -> -c - ---------------------}} > Log[a] >The problem with this is that I need the solution to use normal >'primitive' (if thats the right word) math functions as I need the >formula for a computer program. >With ProductLog being an internal Mathematica function I cant >therefore use this rearrangement. >What can I do so that there is no ProductLog in there? You can't. There is no closed form solution without the ProductLog function or the equivalent with a different name. If you are trying to write program that doesn't depend on Mathematica at runtime and need the solution to a^b - b == c, you will have to either write your own numeric solver or a routine to implement the ProductLog function. -- To reply via email subtract one hundred and four