HP Prime Indefinite Integral useless answer

bbeaver7 · ‎05-11-2017

I wanted to use the CAS system to my advantage to solve indefinite integrals, but I encountered a problem.

when I try to integrate the function

int(xsin(x))

which is the integral ∫(x*sin(x))dx , it just returns

∫xsin(x)dx

and that's just plain useless. I need it to return sin(x) - x*cos(x)

Maké · ‎05-11-2017

Hi!, @bbeaver7:

Syntax :

int(Expr,[Var],[Real1,Real2])

Description :

Integral (definite or indefinite). You can specify a variable of integration as well as the bounds ofr integration. You can use the integration template in the Template menu as well.

Example :

int(1/x) returns ln(abs(x)) int(sin(x),x,0,π) returns 2

Write ... int(x*sin(x)), in Function-CAS

The result, is same. See, the image ...

Kind Regards !.
Have a nice day !.
@Maké (Technical Advisor Premium - HP Program Top Contributor).
Provost in HP Spanish Public Forum ... https://h30467.www3.hp.com/

Tim_Wessman · ‎05-11-2017

Are you entering your multiply between x and sin? Otherwsie, you are trying to integrate the function "xsin(...)" which the CAS can't do (since xsin doesn't exist and the CAS doesn't know how to handle it), so it is returned untouched.

x*sin(...) on the other hand should work fine. Don't leave out * and assume it can be handled. In many cases, your input is ambiguous and the CAS makes the assumption that you are telling it exactly what you want so won't "guess" you mean something else. You very well MIGHT be intending to later define a function named "xsin" which would then be valid for your prior expression.

TW

Although I work for the HP calculator group as a head developer of the HP Prime, the views and opinions I post here are my own.

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