I cannot get the real part of the function

Question

Hossein 2016-6-6

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/288063-i-cannot-get-the-real-part-of-the-function

评论： Walter Roberson 2016-6-14

Hi

I want to get the real part of this long function, but Matlab does not give me the solution, using "real" command. Here is the function which contains two positive symbols which have been defined as "syms e1 e2 positive". Furthermore, I do no know why it does not collect the numbers. I tried "rewrite" command as well but it does not help me in converting "abs" to square way. (sorry about this long function), I did not know how to compact it.

(17592186044416*abs((114122597371621^(1/2)*16204597220848377856^(1/2)*e1^(1/2)*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/766247770432944429179173513575154591809369561091801088)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/766247770432944429179173513575154591809369561091801088)*(4871707714029958889180730753024 - 4871707714029958326230777331712i))/(74069800477562839527407864990178895673762765033*e1^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) - 74069800477562839527407864990178895673762765033*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) - 74069800477562836847602839116461989558801661952*e1*e2^(1/2) - 74069800477562836847602839116461989558801661952*e1^(1/2)*e2 - 74069800477562839527407864990178895673762765033*e1^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 74069800477562839527407864990178895673762765033*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 74069800477562839527407864990178895673762765033*e1^(1/2) - 74069800477562839527407864990178895673762765033*e2^(1/2) + 74069800477562836847602839116461989558801661952*e1*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 74069800477562836847602839116461989558801661952*e1^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 74069800477562836847602839116461989558801661952*e1*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) + 74069800477562836847602839116461989558801661952*e1^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) + 74069800477562839527407864990178895673762765033*e1^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 74069800477562839527407864990178895673762765033*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e1 + 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e2 + 74069800477562836847602839116461989558801661952*e1*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 74069800477562836847602839116461989558801661952*e1^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e1*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e1*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) - 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) + 3444817560549397682511369207808*114122597371621^(1/2)*16204597220848377856^(1/2)*e1^(1/2)*e2^(1/2) + 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e1*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 3444817560549397682511369207808*114122597371621^(1/2)*16204597220848377856^(1/2)*e1^(1/2)*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 3444817560549397682511369207808*114122597371621^(1/2)*16204597220848377856^(1/2)*e1^(1/2)*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) + 3444817560549397682511369207808*114122597371621^(1/2)*16204597220848377856^(1/2)*e1^(1/2)*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544)) + (2^(1/2)*114122597371621^(1/2)*16204597220848377856^(1/2)*e1^(1/2)*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/766247770432944429179173513575154591809369561091801088)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/766247770432944429179173513575154591809369561091801088)*(3444817560549397682511369207808 - 3444817560549397682511369207808i))/(74069800477562839527407864990178895673762765033*e1^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) - 74069800477562839527407864990178895673762765033*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) - 74069800477562836847602839116461989558801661952*e1*e2^(1/2) - 74069800477562836847602839116461989558801661952*e1^(1/2)*e2 - 74069800477562839527407864990178895673762765033*e1^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 74069800477562839527407864990178895673762765033*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 74069800477562839527407864990178895673762765033*e1^(1/2) - 74069800477562839527407864990178895673762765033*e2^(1/2) + 74069800477562836847602839116461989558801661952*e1*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 74069800477562836847602839116461989558801661952*e1^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 74069800477562836847602839116461989558801661952*e1*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) + 74069800477562836847602839116461989558801661952*e1^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) + 74069800477562839527407864990178895673762765033*e1^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 74069800477562839527407864990178895673762765033*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e1 + 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e2 + 74069800477562836847602839116461989558801661952*e1*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 74069800477562836847602839116461989558801661952*e1^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e1*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) - 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e1*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) - 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) + 3444817560549397682511369207808*114122597371621^(1/2)*16204597220848377856^(1/2)*e1^(1/2)*e2^(1/2) + 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e1*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 1722408780274698841255684603904*114122597371621^(1/2)*16204597220848377856^(1/2)*e2*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 3444817560549397682511369207808*114122597371621^(1/2)*16204597220848377856^(1/2)*e1^(1/2)*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544) + 3444817560549397682511369207808*114122597371621^(1/2)*16204597220848377856^(1/2)*e1^(1/2)*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544) + 3444817560549397682511369207808*114122597371621^(1/2)*16204597220848377856^(1/2)*e1^(1/2)*e2^(1/2)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e2^(1/2)*2371823033998011i)/383123885216472214589586756787577295904684780545900544)*exp((2031713442118836966767109806277^(1/2)*182687704666362864775460604089535377456991567872^(1/2)*e1^(1/2)*790607677999337i)/383123885216472214589586756787577295904684780545900544)))^2)/6629077645451087

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Answer 1

Star Strider 2016-6-6

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/288063-i-cannot-get-the-real-part-of-the-function#answer_224660

在 MATLAB Online 中打开

That’s a bit long to copy and paste, so I won’t.

The Symbolic Math Toolbox doesn’t ‘know’ what the real and imaginary parts of your function are because you only told it that:

syms e1 e2 positive

meaning that the real parts of those variables are positive, but that they could be complex. I would use the syms declaration to be:

syms e1 e2 real

to remove that ambiguity, if you want to define those symbolic variables to be real.

With respect to simplifying it, I would use:

x = simplify(x, 'steps',20)
x = vpa(x, 8)

You can of course combine them into one assignment, but keeping them as two statements will let you see the results of each operation.

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Walter Roberson 2016-6-14

The function in your Equation_1segment.m has an infinite number of real roots in pairs that are about 5 apart from each other, with the pairs at increasing intervals.

Walter Roberson 2016-6-14

在 MATLAB Online 中打开

Your function in Equation_1segment.m can be rewritten as

-(764536806725461/36028797018963968) * e1 / ((e1-1)^2*cos((5662050115671473/2251799813685248)*sqrt(e1))-e1^2-6*e1-1) - 8635647223004599/4611686018427387904

or roughly the form -A * f(e1) - B . With those particular constants it comes out as requiring that f(e1) be roughly -0.088244, which happens infinitely often because of the cos but not evenly spaced because of the linear terms. There is no closed form solution for this expression equalling 0.

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