Bug in simplifying trig expressions
08-31-2018, 02:19 PM
Post: #1
 drake200120xx Junior Member Posts: 2 Joined: Aug 2018
Bug in simplifying trig expressions
When trying to use the simplify function in the CAS workspace for "COS(x)/SIN(x)*COT(x)". This should, of course, return COT(x)^2, but instead returned something enormous. For example, part of the numerator of the returned fraction "-16*COS(RE(x))^4*(e^(-IM(x)))^4+16*COS(RE(x))^2..." Does someone know why this happened? Is there a way to fix this or get around it?

Thanks to everyone who helps me out with my new HP Prime

-Drake

(PS-Calculator in Radians and running latest firmware)
08-31-2018, 03:30 PM
Post: #2
 parisse Senior Member Posts: 1,315 Joined: Dec 2013
RE: Bug in simplifying trig expressions
Uncheck complex variables in the CAS settings. Run trigtan instead of simplify if you prefer tan to cos in the answer.
09-01-2018, 02:22 AM
Post: #3
 Magnus512 Junior Member Posts: 23 Joined: Sep 2016
RE: Bug in simplifying trig expressions
There is an error, the calculator says that this is not equal, when I run the same in wolfram it says that it is equal.

09-01-2018, 05:11 AM (This post was last modified: 09-01-2018 05:12 AM by Carsen.)
Post: #4
 Carsen Member Posts: 206 Joined: Jan 2017
RE: Bug in simplifying trig expressions
(09-01-2018 02:22 AM)Magnus512 Wrote:  There is an error, the calculator says that this is not equal, when I run the same in wolfram it says that it is equal.

When you submit the test into the Prime, read the terminal that pops up. I've attached the terminal to this post. Note the "Therefore a==b may return false even if a and b are mathematically equal".

Attached File(s) Thumbnail(s)

09-01-2018, 06:54 AM (This post was last modified: 09-01-2018 06:55 AM by Stevetuc.)
Post: #5
 Stevetuc Senior Member Posts: 313 Joined: Jan 2014
RE: Bug in simplifying trig expressions
(09-01-2018 05:11 AM)Carsen Wrote:
(09-01-2018 02:22 AM)Magnus512 Wrote:  There is an error, the calculator says that this is not equal, when I run the same in wolfram it says that it is equal.

When you submit the test into the Prime, read the terminal that pops up. I've attached the terminal to this post. Note the "Therefore a==b may return false even if a and b are mathematically equal".

It would be much more robust if the prime would check for mathematically equal but different representations and apply
simplify(a-b)==0 itself if need be.
09-01-2018, 08:31 AM
Post: #6
 parisse Senior Member Posts: 1,315 Joined: Dec 2013
RE: Bug in simplifying trig expressions
It seems, but it is not for efficiency reasons : running simplify may take several seconds or more on some expressions. Therefore the choice is left to the user depending on the simplification level in the CAS settings. If you select maximum, then simplify(a-b) is called automatically and you will get 1.
09-01-2018, 08:47 AM
Post: #7
 Stevetuc Senior Member Posts: 313 Joined: Jan 2014
RE: Bug in simplifying trig expressions
(09-01-2018 08:31 AM)parisse Wrote:  It seems, but it is not for efficiency reasons : running simplify may take several seconds or more on some expressions. Therefore the choice is left to the user depending on the simplification level in the CAS settings. If you select maximum, then simplify(a-b) is called automatically and you will get 1.

Thanks, thats useful to know and it works well.
09-01-2018, 06:24 PM (This post was last modified: 09-01-2018 06:25 PM by Magnus512.)
Post: #8
 Magnus512 Junior Member Posts: 23 Joined: Sep 2016
RE: Bug in simplifying trig expressions
That's right my bad jaja I was using min simplification I don't know why
09-02-2018, 03:56 AM
Post: #9
 Tim Wessman Senior Member Posts: 2,293 Joined: Dec 2013
RE: Bug in simplifying trig expressions
Because that is the default and you should be using it. We will be removing "maximum". All it really does it click the simplify button each time essentially.

TW

Although I work for HP, the views and opinions I post here are my own.
09-02-2018, 05:40 AM
Post: #10
 CyberAngel Member Posts: 299 Joined: Jul 2018
RE: Bug in simplifying trig expressions
(09-02-2018 03:56 AM)Tim Wessman Wrote:  Because that is the default and you should be using it. We will be removing "maximum". All it really does it click the simplify button each time essentially.

Why remove it?
Let the USER choose!!
Make a better help - don't remove options.
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