Trig Error in CAS

02122016, 06:42 PM
(This post was last modified: 02122016 07:06 PM by chazzs.)
Post: #1




Trig Error in CAS
Can anyone explain to me (or recreate the bug) why acos(cos(2)) = 2pi  2, and not 2, which you get when evaluating acos(cos(2.)). Works fine on the home side.
It seems 1 is the only (integer) value that is correct: acos(cos(1))=1. Worse is acos(cos(4)) = 2 pi + 4 = 2.2831 (Should be positive, or 2 pi  4). These are all in radian mode. Degree mode seems to work fine. A little troubling, or I'm missing something. C 

02122016, 10:19 PM
(This post was last modified: 02122016 10:21 PM by DrD.)
Post: #2




RE: Trig Error in CAS
Wolfram says: http://www.wolframalpha.com/input/?i=aco...%284%29%29
Here is my screenshot (Exact mode toggled): 

02132016, 12:30 AM
Post: #3




RE: Trig Error in CAS  
02132016, 03:29 AM
(This post was last modified: 02132016 09:15 PM by compsystems.)
Post: #4




RE: Trig Error in CAS
HOME MODE (CNES ): Computer Numeric Expert System
ACOS(COS(4)) [ENTER] 2.28318530718 ok acos(cos(4)) [ENTER] 2.28318530718 ok CAES MODE: Computer Algebra Expert System flag on: Simplify Maximum ACOS(COS(4)) [ENTER] 2*π+4 approx(Ans) −2.28318530718 ? acos(cos(4)) [ENTER] 2*π+4 approx(Ans) −2.28318530718 SUGGESTION FOR THE FOLLOWING FIRMWARE for CAS mode, show history with 2 outputs (Exact result & Decimal Approximation) , as does wolfram CAS ACOS(COS(4)) [ENTER] ____________________ 2*π4 ____________________ 2.28318530718 Is a good idea? 

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