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How to use Reduce to find com

Posted 9 years ago

I tried to solve the following set of equations $$- v_+ = C_1 \sinh (C_2) \\ -v_+ = \sinh(-s_+ q + C_2), $$ where $v_+$, $s_+$ and $q$ are constants and I try to solve for $C_1$ and $C_2$ using this code line - Solve[-vplus == C*sinh[B] && -vplus == C*sinh[-S*q + B], {C, B}] But I get this message - Inverse functions are being used by Solve, so some solutions may not \ be found; use Reduce for complete solution information

How can I use Reduce here to get complete solution?

POSTED BY: Omer Tzuk
3 Replies

You wrote the equations in Latex in one form, then in the Mathematica code you used different symbols. little confusing. Let me write your equations, and instead of using -v, just use v since it is the same. And used lowerCaseLetters. Since C is actually a Mathematica symbol. Not a good idea to use UpperCase first letter in Mathematica. So your equations are basically these

        eq = {v == c1*Sinh[c2], v == Sinh[-s q + c2]}

To use Reduce

       Reduce[eq, {c1, c2}, Reals]

And to obtain a solution with no warnings

       Solve[eq, {c1, c2}, Reals]
POSTED BY: Nasser M. Abbasi
Posted 9 years ago

Thank you very much for the corrections Nasser! It does though give me a message that this equations cannot be solved with the methods available to Solve. But I don't understand from the explanations which of the other functions can solve this type of system of equations..

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POSTED BY: Omer Tzuk

I forgot one line. I had to convert to exponential form first and forgot to paste the line.. If you can try this. No warnings. V 10.02.

ClearAll[c1, c2, s, q];
eq = { v + c1*Sinh[c2] == 0 , v +  Sinh[-s*q + c2] == 0};
eq = TrigToExp[eq];
Reduce[eq, {c1, c2}, Reals]
Solve[eq, {c1, c2}, Reals]

enter image description here

POSTED BY: Nasser M. Abbasi
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