Integration failure

08212016, 10:14 PM
Post: #1




Integration failure
Int (ln(tan(X)))/((sin(X))(cos(X))) returns the integral
TI NSpire returns ((ln(tan(X)))^2)/2 Both return same answer in approximate mode. 

08212016, 10:23 PM
Post: #2




RE: Integration failure
...that is, when made into a definite integral!


08222016, 03:50 AM
Post: #3




RE: Integration failure
(08212016 10:14 PM)lrdheat Wrote: Int (ln(tan(X)))/((sin(X))(cos(X))) returns the integral Are you sure the parentheses in your input are correct? As shown, the integral ends before the division sign, which I suspect is not what you wanted. <0ɸ0> Joe 

08222016, 06:09 AM
Post: #4




RE: Integration failure
If you derive (ln(tan(x)))^2, there should be a (1+tan(x)^2) term, but I don't see it in your input (which has strange parenthesis and missing * sign).


08222016, 08:30 AM
Post: #5




RE: Integration failure
Hello Bernard.
Using 1+tan^2 = 1/cos^2, the derivative of ((ln(tan(x))^2)/2 is ln(tan(x))/(sin(x)*cos(x)), which is what I think the original poster meant. I have no Prime to verify though. Cheers, Werner 41CV†,42S,48GX,49G,DM42,DM41X,17BII,15CE,DM15L,12C,16CE 

08222016, 10:20 AM
Post: #6




RE: Integration failure  
08222016, 12:27 PM
Post: #7




RE: Integration failure
Hi!
This is what I get (with 10077). Irdheat is OK. Marcel. 

08222016, 04:07 PM
Post: #8




RE: Integration failure
Xcas also behaves the same. Thanks!
TW Although I work for HP, the views and opinions I post here are my own. 

08222016, 06:14 PM
Post: #9




RE: Integration failure
Then you can solve it with trigtan
a:=int(ln(tan(x))/(sin(x)*cos(x))); trigtan(a) 

08242016, 08:30 PM
Post: #10




RE: Integration failure  
08252016, 05:58 AM
Post: #11




RE: Integration failure
This is unrelated, but thanks for the bug report!


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