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Bug introduced in 12.0 and fixed in 12.1


After upgrading to mathematica 12, this integral gives the wrong result, also with other types of similar integrals.

Integrate[t[2]*Exp[t[2]],t[2]] 

The output

Exp[t[2]^2]/2

is wrong (it should be E^t[2] (-1 + t[2])). Such problem does not exist in previous versions.

PS, I have to use a lot of t[i] in my program, even if I change the [i] to subscripts, the problem is still there.

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  • 2
    $\begingroup$ It is interesting to note that if I pick a variable without index, then it gives you what you expect. In other words, Integrate[blah*Exp[blah], blah] gives (-1 + blah) E^blah as you expect. OK, a new wrinkle: when using the t[2], I notice that it doesn't properly highlight the variables over which we are integrating. $\endgroup$ – Mark R Nov 8 '19 at 0:30
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    $\begingroup$ Integrate[t[1] Sin[t[1]], t[1]] fails, but Integrate[t@Hold[2]*Exp[t@Hold[2]], t@Hold[2]] succeeds. $\endgroup$ – Michael E2 Nov 8 '19 at 2:29
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    $\begingroup$ Please report the issue to the support. $\endgroup$ – Alexey Popkov Nov 8 '19 at 15:31
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Fixed in 12.1


Mathematica graphics


ClearAll[t];
Integrate[t[2]*Exp[t[2]], t[2]]
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