Incorrect values with some trigonometric functions

08032018, 10:43 PM
(This post was last modified: 08032018 10:49 PM by jeanjpersia.)
Post: #1




Incorrect values with some trigonometric functions
I don't have too much time with this my HP prime rev:C and in an exam, I realized that when I try to put things like Cos(π/2) the answer is not the number that I want, I have a similar problem with graphics if I put the cursor in (1,0) the calculator says that I have in (0.99999999,0).
If someone knows what I need to change in settings to solve the problem, it would be great. thanks in advance! Here an example: https://imgur.com/649PMSj 

08042018, 06:52 AM
Post: #2




RE: Incorrect values with some trigonometric functions
I think you need to go to CAS mode to get the correct result and set the angle measure to radians in the Home Settings
Best, Aries 

08042018, 07:28 AM
(This post was last modified: 08042018 07:29 AM by Stevetuc.)
Post: #3




RE: Incorrect values with some trigonometric functions
(08042018 06:52 AM)Aries Wrote: I think you need to go to CAS mode to get the correct result and set the angle measure to radians in the Home Settings The small error will still exist in home mode though. It exists in the Casio too but the casio rounds such residual errors in trig functions to 0 to present a clean result. The Prime is more honest. Maybe for educational use, there could be a user flag that toggles this behaviour so that say a trig result below a threshold < 1e11 say, is displayed as 0. 

08042018, 09:26 AM
Post: #4




RE: Incorrect values with some trigonometric functions
(08042018 07:28 AM)Stevetuc Wrote:(08042018 06:52 AM)Aries Wrote: I think you need to go to CAS mode to get the correct result and set the angle measure to radians in the Home Settings Y' know, Home = numerical and CAS = symbolic, on any numerical calculator getting a nonzero result (for cos(pi/2)) is an acceptable solution, as PI cannot be represented numerically. This is where CAS comes into play, as a symbolic solver. As you said, the Prime is more honest in this respect. Best, Aries 

08042018, 10:39 AM
(This post was last modified: 08042018 10:40 AM by Stevetuc.)
Post: #5




RE: Incorrect values with some trigonometric functions
(08042018 09:26 AM)Aries Wrote:(08042018 07:28 AM)Stevetuc Wrote: The small error will still exist in home mode though. It exists in the Casio too but the casio rounds such residual errors in trig functions to 0 to present a clean result. The Prime is more honest. Maybe for educational use, there could be a user flag that toggles this behaviour so that say a trig result below a threshold < 1e11 say, is displayed as 0. Indeed. I was targeting home mode in my comments. Any calc not showing an error here (numeric mode) is truncating or rounding the error. Im happy to see the error, but I can understand the comforting feeling to see cos(pi/2)=0, which is why the casio presents it as such even for a numeric calculation! 

08042018, 01:42 PM
Post: #6




RE: Incorrect values with some trigonometric functions  
08042018, 06:30 PM
Post: #7




RE: Incorrect values with some trigonometric functions  
08052018, 03:04 AM
Post: #8




RE: Incorrect values with some trigonometric functions
Also note that you can quickly toggle your angle settings by tapping near the clock, and then on the appropriate angle symbol.
TW Although I work for HP, the views and opinions I post here are my own. 

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