Re: using units with FindRoot

• To: mathgroup at smc.vnet.net
• Subject: [mg124521] Re: using units with FindRoot
• From: Bob Hanlon <hanlonr357 at gmail.com>
• Date: Sun, 22 Jan 2012 07:26:23 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201201211016.FAA10141@smc.vnet.net>

```You can eliminate the units by replacing them with one.

FindRoot[eqns /. Celsius -> 1, ...]

Bob Hanlon

On Sat, Jan 21, 2012 at 5:16 AM, Michelle A <hfvballgurl33 at gmail.com> wrote:
> Is there a way to use FindRoot with units?  I'm solving the radiation
> equation with a Temp^4.  Solve takes too long/doesn't finish the
> system of equations solution.  It gives the error that {T,10Celsius}
> is not a number or array of numbers.
>
> I have 4 equations and 4 unknowns.  The first 3 equations are linear
> the last one is in the form: sigma((Troof+273Celsius)^4-(Tattic
> +273Celsius)^4)/R=Q (This isn't the whole equation, just a simplified
> form of it)
>
> Troof, Tattic, and Q are 3 of my unknowns.
>
> Is the only way to resolve this to divide by the units for each
> parameter (ex. Troof/Celsius+273)?
>

```

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