Solve Logrithm Equation with multiple solutions

2012 9 14
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I am trying to solve an equation using:
solve('(1.581/1.5)=x*log(58/x)')
ans =
56.936183721096301740573270965739
However, there is another solution 0.183, which matlab does not give me and that happen to be the solution I need. How to solve it? Thanks!

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Matt Fig
Matt Fig 2012-9-14

2 个投票

Just use numerical methods:
f = @(x)(1.581/1.5)-x.*log(58./x);
rt = fzero(f,.2)

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Matt Fig
Matt Fig 2012-9-14
Carol comments,
"Thanks Matt, so the trick is for discontinuous function, you got to define the range for its solution?"
Matt Fig
Matt Fig 2012-9-14
When using FZERO you have to supply an initial guess or a bracket. See the help for more information.
help fzero

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