Confusing derivative(sqrt(1sinx)) result Bug? [SOLVED]

05042018, 09:12 PM
(This post was last modified: 05272018 12:28 PM by vvolkan.)
Post: #1




Confusing derivative(sqrt(1sinx)) result Bug? [SOLVED]
Derivative of sqrt(1sinx) should be cosx/2sqrt(1sinx) but it returns a long confusing result and it cant be simplified.


05052018, 07:48 AM
Post: #2




RE: Wrong derivative(sqrt(1sinx)) result Bug?
As I get everything correct in CAS on the emulator you should show us a screenshot.
Arno 

05052018, 09:24 AM
(This post was last modified: 05052018 01:46 PM by vvolkan.)
Post: #3




RE: Wrong derivative(sqrt(1sinx)) result Bug?
Hi Arno,
I tried on HP Prime Pro app and pc(both rev.13441),same result. Here are the screenshots from pc. Volkan 

05052018, 10:15 AM
(This post was last modified: 05052018 10:20 AM by DrD.)
Post: #4




RE: Wrong derivative(sqrt(1sinx)) result Bug?  
05052018, 10:45 AM
Post: #5




RE: Wrong derivative(sqrt(1sinx)) result Bug?  
05052018, 12:43 PM
(This post was last modified: 05052018 12:47 PM by parisse.)
Post: #6




RE: Wrong derivative(sqrt(1sinx)) result Bug?
sqrt(1sin(x)) is autosimplified to sqrt(2)*abs(sin(pi/4+x/2)), because it's much better not to deal with "false" sqrt, for example if you want to integrate sqrt(1sin(x)).
The derivative is sqrt(2)*cos(x/2pi/4)*abs(sin(x/2pi/4))/(2*sin(x/2pi/4)), it looks complicated but it is not: it's the product of a cos by a sign. If you make assumptions on x like assume(x>0 && x<pi/2), you will not get absolute values, and the derivative is simpler sqrt(2)*cos(x/2pi/4)/2 

05052018, 01:43 PM
(This post was last modified: 05052018 03:33 PM by vvolkan.)
Post: #7




RE: Wrong derivative(sqrt(1sinx)) result Bug?
It seems as calc gives different variation of result if "√" is used instead of "^1/2" for this derivative. Thanks parisse for comprehensive explanation.


05052018, 07:24 PM
(This post was last modified: 05052018 10:57 PM by vvolkan.)
Post: #8




RE: Wrong derivative(sqrt(1sinx)) result Bug?
(05052018 10:15 AM)DrD Wrote:(05042018 09:12 PM)vvolkan Wrote: Derivative of sqrt(1sinx) should be cosx/2sqrt(1sinx) but it returns a long confusing result and it cant be simplified. Hi DRD, I forgot to write the negative sign. I edited the main post. I shared screenshots to clarify the problem. Thanks 

05052018, 09:15 PM
Post: #9




RE: Wrong derivative(sqrt(1sinx)) result Bug?  
05062018, 06:40 AM
Post: #10




RE: Wrong derivative(sqrt(1sinx)) result Bug?
Another way to get it: sqrt(asin(x))'


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