Re: unwanted Complex result

• To: mathgroup at smc.vnet.net
• Subject: [mg91596] Re: [mg91589] unwanted Complex result
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Thu, 28 Aug 2008 07:39:27 -0400 (EDT)
• Reply-to: hanlonr at cox.net

```soln = Solve[(Sqrt[speed^2 - windx^2] + windy)/a
speed^2 + b speed + c == distance/height, speed];

Select[soln /.
{windx -> 1, windy -> 1, a -> 1, b -> 1, c -> 1,
distance -> 20, height -> 5} // N,
FreeQ[#, Complex] &]

{{speed->-1.46762},{speed->1.11901}}

Bob Hanlon

---- John Rivers <first10 at btinternet.com> wrote:

=============
Solve[
(Sqrt[speed ^ 2 - windx ^ 2] + windy) / a speed ^ 2 + b speed + c ==
distance / height
, speed]

this works but returns 4 solutions that all return complex numbers

I need a real number

how do I:

- convert a complex result into real number
or
- solve the equation to give only real numbers

```

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