*To*: mathgroup@smc.vnet.net*Subject*: [mg12014] Re: calculation*From*: Paul Abbott <paul@physics.uwa.edu.au>*Date*: Fri, 17 Apr 1998 03:40:50 -0400*Organization*: University of Western Australia*References*: <6gr69a$8lo@smc.vnet.net>

Saeed Esmaily Rashid wrote: >I have an equation > > .001422409738*R^(73/80)*(R^(1/2)-1)^(-13/40) == .04 > > i'm using the Solve function in Mathematica 3.0 to solve it for R, but > it calculats endlessly and takes very long time. I turns out that Mathematica cannot solve the general problem a*R^p*(R^(1/2)-1)^c == d It is easy to construct transcendental equations with no simple closed-form solution. Perhaps you should look at a plot, e.g., In[1]:= eq=.001422409738*R^(73/80)*(R^(1/2)-1)^(-13/40) == .04; In[2]:= Plot[Evaluate[Subtract@@eq],{R,1,100}]; Then you can use FindRoot to find the numerical solutions you are after: In[3]:= FindRoot[eq,{R,1.0001}] Out[3]= {R -> 1.00007} In[4]:= FindRoot[eq,{R,80}] Out[4]= {R -> 81.2655} Cheers, Paul ____________________________________________________________________ Paul Abbott Phone: +61-8-9380-2734 Department of Physics Fax: +61-8-9380-1014 The University of Western Australia Nedlands WA 6907 mailto:paul@physics.uwa.edu.au AUSTRALIA http://www.pd.uwa.edu.au/~paul God IS a weakly left-handed dice player ____________________________________________________________________