[Maxima-bugs] [ maxima-Bugs-1950294 ] more on integrate(1/cosh(a*x)^2, x, -inf, inf)

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Bugs item #1950294, was opened at 2008-04-23 21:41
Message generated for change (Comment added) made by robert_dodier
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>Category: Lisp Core - Integration
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: more on integrate(1/cosh(a*x)^2,x,-inf,inf)

Initial Comment:
integrate(1/cosh(3*x)^2,x,-inf,inf);

returns

Division by 0 -- an error.  To debug this try debugmode(true);

integrate(1/cosh(4*x)^2,x,-inf,inf);

returns

 << Expression too long to display! >>

Eric

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>Comment By: Robert Dodier (robert_dodier)
Date: 2008-06-21 19:41

Message:
Logged In: YES 
user_id=501686
Originator: NO

Observed in 5.15.0cvs.

integrate(1/cosh(a*x)^2,x,-inf,inf);
 => asksign about a; response=p => 0, obviously incorrect

When asksign response is n, then p (2nd question about exp(a) - 1),
integrate prints "Principal value" and the result is -2/a, which might be
correct (to guess from quad_qags results). But various other combinations
of asksign responses give 0.


integrate(1/cosh(3*x)^2,x,-inf,inf);
 => division by 0 as reported above

integrate(1/cosh(4*x)^2,x,-inf,inf);
 => very long expression w/ trig and hyperbolic functions
%, numer;
 => - 1.599481181895906E+15 obviously incorrect



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