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Re: Problem trying to Solve for 'theta' ... v6.01

  • To: mathgroup at smc.vnet.net
  • Subject: [mg84804] Re: Problem trying to Solve for 'theta' ... v6.01
  • From: Bill Rowe <readnewsciv at sbcglobal.net>
  • Date: Tue, 15 Jan 2008 03:15:22 -0500 (EST)

On 1/14/08 at 6:50 AM, lrebanks at netvigator.com (Lea Rebanks) wrote:

>I am having a problem trying to solve for 'theta' & cannot find the
>appropriate function / method to do this. I am using Mathematica
>version 6.01 on a PC.   Any advice gratefully received.

>PS - pasted coding below.

>Solve[2 (-1+IntegerPart[1+q/360])
>IntegerPart[1+q/360]+IntegerPart[1+q/360]
>Mod[IntegerPart[q/90],4]+1/Csc[=B0 (135-Mod[q,90])]
>IntegerPart[1+q/360] Sin[=B0 Mod[q,90]]*Value,q]

Several comments. First, it is greatly preferred that you first
convert code to input form before pasting into email. That way,
anyone trying to review your code can easily paste it into
Mathematica. If you do not first convert to input form, things
that do not have a simple ASCII form get changed into something
not readily recognizable.

Next, Value is a reserved system symbol as can be seen by executing

?Value

in a fresh session. You should not be using this as a variable
name. In general, it is good practice to use lower case letters
for the start of you variable names since this is guaranteed to
prevent conflicts of this nature.

Look at the documentation and syntax for Solve. You need to
provide as arguments an equation and a list of variables. You
have not done so. The first argument you have provided is an
expression, not an equation. And your second argument asks only
for the solution for q not theta.

Finally, Solve is primarily intended to solve polynomial
equations. It will generally work for simple non-polynomial
equations usually generating a warning about using inverse
functions. Assuming what you meant to do is have the expression
you provided above equal some constant, the resulting equation
is clearly non-polynomial in the variables and does not look
like one of the simple cases Solve will be able to handle.

I am guessing you want a numerical rather than symbolic
solution. If so, look at using NMaximize, NMimimize or FindRoot
here instead of Solve.
--
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