Bug report - solve([sin(cos(x))/cos(x)==0],x) gives wrong result

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Jun 27, 2014, 5:26:36 PM6/27/14

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Hi there,

solve([sin(cos(x))/cos(x)==0],x) gives:

[x == 1/2*pi]
which is wrong. There is no solution. 


See plot(sin(cos(x))/cos(x),(-pi,pi))

Best regards,
Christoph Jentzsch

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Jun 30, 2014, 10:10:30 AM6/30/14

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On Friday, June 27, 2014 5:26:36 PM UTC-4, Christoph Jentzsch wrote:

Hi there,

solve([sin(cos(x))/cos(x)==0],x) gives:
[x == 1/2*pi]
which is wrong. There is no solution. 

Thanks for reporting this.


See plot(sin(cos(x))/cos(x),(-pi,pi))

Well, in any case solve isn't supposed to be taking limits or anything, this function is undefined at pi/2!

$ ./sage -maxima

<snip>

using Lisp ECL 12.12.1

Distributed under the GNU Public License. See the file COPYING.

Dedicated to the memory of William Schelter.

The function bug_report() provides bug reporting information.

(%i1) solve(sin(cos(x))/cos(x) = 0, x);

solve: using arc-trig functions to get a solution.

Some solutions will be lost.

%pi

(%o1) [x = ---]

(%i2)

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