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I tried to execute this simple command

Plot[Cosh[t] - Sinh[t] + Sin[t], {t, 0, 40}]

and this is the result I got

enter image description here

As you can see, there is an unexpected visual between $t=30$ and $t=40$. But when I used the identity $e^{-t}=\cosh{t}-\sinh{t}$, everything went fine. This command

Plot[Exp[-t] + Sin[t], {t, 0, 40}]

gives

enter image description here

What's going on here? Can anyone reproduce this result? Is this a bug? I'm using MMA 12 64bit on Windows 10.

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  • $\begingroup$ Try the MaxRecursion option for Plot. It is generally used to control adaptive sampling. $\endgroup$ – Lotus Feb 9 at 10:30
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    $\begingroup$ Both $\cosh x$ and $\sinh x$ functions are diverging at large positive $x$ as $e^x$. For these values are hard to achieve perfect cancellation between the two functions. $e^{-x}$ does not have this problem. Use WorkingPrecision -> 30 option of Plot to get the same result. $\endgroup$ – yarchik Feb 9 at 10:57
  • $\begingroup$ Plot[Cosh[t] - Sinh[t] + Sin[t], {t, 0, 40}, PlotPoints -> 4] this can partly solve it. $\endgroup$ – wuyudi Feb 9 at 15:35
  • $\begingroup$ The same happens for me (v11 on Windows 10), WorkingPrecision -> 20 corrects it. $\endgroup$ – მამუკა ჯიბლაძე Feb 10 at 7:25
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I think there is a problem with your main file. I tried your command and the result is ok. My Mma version is 12.

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