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MathGroup Archive 1995

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Re: Simple problem for math wiz

  • To: mathgroup at christensen.cybernetics.net
  • Subject: [mg1708] Re: Simple problem for math wiz
  • From: porfy at odin.gsfc.nasa.gov (Porfirio Beltran)
  • Date: Wed, 19 Jul 1995 00:13:39 -0400
  • Organization: NASA Goddard Space Flight Center -- Greenbelt, Maryland USA

In article <DBKwIr.2qv at wri.com>, nomail at me.net (REVEAL) wrote:

> Anyone here know how to find the solution set to: sin^2x+sinx-1=0 ? the
trick, that is?
> (limited to trig & algebra)

Is this is the function you want to solve?

In[1]    Sin[x]^2 + Sin[x] - 1 == 0
Out[1]   -1 + Sin[x] + Sin[x]^2 == 0

If so, I'm sure you know that the Mma Function 'Solve' doesn't cut it:

In[2]    Solve[Sin[x]^2 + Sin[x] - 1 == 0]
Out[2]   {{Sin[x] -> (-1 - 5^(1/2))/2},{Sin[x] -> (-1 + 5^(1/2))/2}}

Use 'FindRoot':

In[3]    FindRoot[Sin[x]^2 + Sin[x] - 1 == 0, {x,0}]
Out[3]   {x -> YOU FIND IT!}

Porfy.

** "Because is my nature..." - The Scorpion. **


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