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How can I solve an equation using constants defined outside the solve command?

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Lynn
Lynn 2014-4-8
关闭： MATLAB Answer Bot 2021-8-20
Hi, I have the following code:
solve('(.5*Tp(i)+ .5*T1)/(Tp(i)/(2*pi)) = x - e(i)*sin(x)' , '-pi/2 < x < pi/2');
where Tp, and e are taken from arrays. I get the following error:
Warning: Could not extract individual solutions. Returning a MuPAD set object. > In solve>assignOutputs at 104 In solve at 87.
When I plug in manually the values for Tp, and e, I get an answer, so the problem seems to be the face that these constants are defined outside the prompt command. How can I fix this? Note that I have an old version of matlab, so I can't use some 2014a commands. Thanks for you help!

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回答（1 个）

Walter Roberson
Walter Roberson 2014-4-8
syms x
solve( (.5*Tp(i)+ .5*T1)/(Tp(i)/(2*pi)) = x - e(i)*sin(x) , '-pi/2 < x < pi/2');
If that gives you trouble then
syms x
solve((.5*Tp(i)+ .5*T1)/(Tp(i)/(2*pi)) - (x - e(i)*sin(x)) , '-pi/2 < x < pi/2');
  2 个评论
Lynn
Lynn 2014-4-8
The first one gave me the same error, and the second one gave me the error: Warning: 2 equations for 1 variables. Explicit solution could not be found.
Walter Roberson
Walter Roberson 2014-4-8
When you call solve() from the MATLAB level, each part must be either a variable name, or a name/value pair, or a symbolic equation. Your '-pi/2 < x < pi/2' is not any of those: it is a symbolic inequality.
You could try using assumptions with assume(), or you could call into the symbolic engine's solve() function using
feval(symengine, 'solve', ......)

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