[CAS] arc sine of a complex number

12172014, 02:45 AM
Post: #1




[CAS] arc sine of a complex number
[home mode]
ASIN(4.0+i) => 1.31861691808+2.09659645729*iok [CAS mode] ASIN(4.0+i) => "Error: Bad Argument Value" why the argument is a bad 

12172014, 03:07 AM
Post: #2




RE: [CAS] arc sine of a complex number
What are your flag settings? I get, in CAS, ASIN(4+i) unevaluated, and ASIN(4.+i) 1.31... + 2.09...*i, no problem.


12172014, 03:17 AM
Post: #3




RE: [CAS] arc sine of a complex number
[CAS mode] and use i (set)
ASIN(4.0+i) => 1.31861691808+2.09659645729*i ok sorry for my bad English I think that instead of showing the error message "Error: Bad Argument Value" , should say set flag "use i" "use i" says use i to factor polynomials that relation has polynomials with complex numbers? 

12172014, 03:24 AM
Post: #4




RE: [CAS] arc sine of a complex number
(12172014 03:17 AM)compsystems Wrote: [CAS mode] and use i (set) Perhaps the CAS interprets (4+i) as a polynomial (of degree 0) with complex coefficients. (Just a guess on my part) Graph 3D  QPI  SolveSys 

12172014, 03:25 AM
(This post was last modified: 12172014 03:28 AM by Helge Gabert.)
Post: #5




RE: [CAS] arc sine of a complex number
I see what you are suggesting, but it could be very exhausting to come up with precise error messages for every eventuality a user could encounter. Yes, here you need to check "Use i."


12172014, 03:45 AM
(This post was last modified: 12172014 03:53 AM by compsystems.)
Post: #6




RE: [CAS] arc sine of a complex number
Messages that launches the hpprime are truly disappointing. =(
Is required an expert administrator user flags, a common user to read the argument is "Bad Argument Value", ask why. I ask because the input argument is a bad value? entry is a valid complex number. or should I ask switch flag to answer complex, as it does in the HP50 asin("hello") => "Error: Bad Argument Value" OK but not ASIN(4.0+i) => "Error: Bad Argument Value" :~( 

12172014, 03:50 AM
Post: #7




RE: [CAS] arc sine of a complex number
I don't disagree . . . flag switching like in the HP50G might be more desirable in this case.


12172014, 06:53 AM
Post: #8




RE: [CAS] arc sine of a complex number
i is complex mode, I'm not responsible for the way it is described on the HP settings screen.
I'll have a look, perhaps I can improve the error message. 

12172014, 07:51 AM
Post: #9




RE: [CAS] arc sine of a complex number
Well, I will probably remove the error, since it is only present on the Prime, not in Xcas.


12172014, 04:20 PM
(This post was last modified: 12172014 04:57 PM by compsystems.)
Post: #10




RE: [CAS] arc sine of a complex number
(12172014 06:53 AM)parisse Wrote: i is complex modeWhat is the difference between the flags "Complex" and "use I"? The message that launches the hpprime (asin(4.0+i) => "Error: Bad Argument Value" ) makes losing all the computational power of xcas (12172014 07:51 AM)parisse Wrote: Well, I will probably remove the error Return the same input when the flag is disabled, suggests you can not solve. :~( asin(4.0+i) => asin(4.0+i) =( ideally show a dialog box saying that if you want to change a complex mode, this is already implemented in the CAS of HP50, what involution? must extract the best from the past HP50G are you agree with this request? +1 or 1 or indifferent, please vote solve(x^2+2*x+3 = 0,x) "use i [OFF]" => [] ok no real results solve(x^2+2*x+3 = 0,x) "use i [on]" => {√(2)*i1,√(2)*i1} solve(x^2+2*x+3 = 0,x) "use i [OFF]" => great if also generates a message to change the flag, if the user does not want to change return [] PD: Please Parisse can improve the output of the expression, ordered the real part first solve(x^2+2*x+3 = 0,x) "use i [on]" => {1+ √(2)*i, 1  √(2)*i1 } Naturally mathematical texts show real part + imaginary part , a+b*I, also for easy reading when the output expression is very large other request is to label the output only for the purpose of observing a more didactic output, this may be adding a new flag in configuration of the CAS solve(x^2+2*x+3 = 0,x) "use i [on] and tag[on]" => { x1:1+ √(2)*i, x2:1  √(2)*i1 } Thanks 

12172014, 06:56 PM
Post: #11




RE: [CAS] arc sine of a complex number
"Use i for factoring" is more restrictive than what complex mode does. For example, if complex mode is on, sqrt(x^2) returns x instead of x. On the HP port of giac, some functions like ln were returning errors if the argument would return a complex answer (like domain error on the TI) in non real mode. This was later removed, but I did not check everything, and functions that are not used often like asin/acos have the check.
For the mode switch, my experience with the hp49/50/40 convinced me it was not such a good idea because it requires manual mode switchs after. For example if you make a parametric plot on the 50g, you end up in complex approx mode, and you must switch back to real exact for normal CAS operations (there are shortcuts to do that but nongeeks will not learn them). 

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