Re: calculation
- To: mathgroup@smc.vnet.net
- Subject: [mg11998] Re: calculation
- From: "John M. Jowett" <John.Jowett@cern.ch>
- Date: Fri, 17 Apr 1998 03:40:34 -0400
- Organization: CERN
- References: <6gr69a$8lo@smc.vnet.net>
Saeed Esmaily Rashid wrote:
>
> Hello!
>
> My name is Saeed and i'm studying physics. I have a problem which ihope
> someone can help me with it. 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. the question is that
> is there any way to optimize this equation or using another function
Hello,
This is a numerical problem so use FindRoot, not Solve,
FindRoot[.001422409738*R^(73/80)*(R^(1/2)-1)^(-13/40) == .04,{R,2}]
and you'll get
{R->81.268}
Plotting the function also helps. Try
Plot[.001422409738*R^(73/80)*(R^(1/2)-1)^(-13/40) - .04,{R,0,100}]
and you'll find another root close to the singularity
FindRoot[.001422409738*R^(73/80)*(R^(1/2)-1)^(-13/40) ==
.04,{R,1.00001}]
{R->1.00007}
You can also try using the option WorkingPrecision (if you know that it
is justified).
John Jowett
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