Opened 21 months ago

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

Reported by: Owned by: Gaël Cousin major sage-9.8 calculus N/A

### 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.

### 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-9.3 → sage-9.4

Moving to 9.4, as 9.3 has been released.

### comment:3 Changed 15 months ago by Matthias Köppe

Milestone: sage-9.4 → sage-9.5

### comment:4 Changed 12 months ago by Matthias Köppe

Milestone: sage-9.5 → sage-9.6

### comment:5 Changed 7 months ago by Matthias Köppe

Milestone: sage-9.6 → sage-9.7

### comment:6 Changed 2 months ago by Matthias Köppe

Milestone: sage-9.7 → sage-9.8
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