Opened 21 months ago

Last modified 2 months ago

#31506 new defect

(sinh(sqrt(t))).laplace(t,s) returns 0

Reported by: Gaël Cousin Owned by:
Priority: major Milestone: sage-9.8
Component: calculus Keywords:
Cc: Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

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Description

On sage-9.1 SageMath version 9.1, Release Date: 2020-05-20 Using Python 3.7.3.

Built in Centos 8, I meet the following behavior.

sage:(sinh(sqrt(t))).laplace(t,s)
0

I don't get 0 with other (non zero) functions.

Change History (6)

comment:1 Changed 21 months ago by Dave Morris

I confirm the bug (on MacOS 10.15.7 and Ubuntu 20.04). As a workaround, you can use sympy:

sage: var("s t")
(s, t)
sage: laplace(sinh(sqrt(t)), t, s, algorithm="sympy")[0]
1/2*sqrt(pi)*e^(1/4/s)/s^(3/2)

The problem (as with some other bugs) seems to be our default setting of domain : complex for maxima:

sage: maxima("laplace(sinh(sqrt(t)), t, s);")  # maxima gives the wrong answer
0
sage: maxima("domain : real;")  # change the domain
real
sage: maxima("laplace(sinh(sqrt(t)), t, s);")  # now we get the right answer
(sqrt(%pi)*%e^(1/(4*s)))/(2*s^(3/2))

PS I get the same behavior in a command-line maxima session (correct answer when the domain is "real" and 0 when the domain is "complex").

comment:2 Changed 19 months ago by Matthias Köppe

Milestone: sage-9.3sage-9.4

Moving to 9.4, as 9.3 has been released.

comment:3 Changed 15 months ago by Matthias Köppe

Milestone: sage-9.4sage-9.5

comment:4 Changed 12 months ago by Matthias Köppe

Milestone: sage-9.5sage-9.6

comment:5 Changed 7 months ago by Matthias Köppe

Milestone: sage-9.6sage-9.7

comment:6 Changed 2 months ago by Matthias Köppe

Milestone: sage-9.7sage-9.8
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