Integral question
05-28-2014, 08:20 PM
Post: #1
 lrdheat Senior Member Posts: 823 Joined: Feb 2014
Integral question
New version...

Integral from 1 to 2 of (x+1)*(x^2+2*x+2)^(1/3) returns the unevaluated integral in CAS. When using surd, I get a message: temporary replacing surd/nthroot by fractional powers. I then get the unevaluated integral back.

In home, and in plot, I immediately get the numeric equivalent.

Why won't this evaluate in CAS as it is the equivalent of of the integral from 1 to 2 of u^(1/3)*du/2?
05-29-2014, 03:12 AM
Post: #2
 Helge Gabert Senior Member Posts: 467 Joined: Dec 2013
RE: Integral question
Did this work in the 5447 firmware?

On the HP50g, the definite integral between 1 and 2 returns an exact answer, and INTVX returns the symbolic answer for the indefinite integral without any problems.

Maybe try integration by parts . . .
05-29-2014, 05:20 AM
Post: #3
 lrdheat Senior Member Posts: 823 Joined: Feb 2014
RE: Integral question
Using int() didn't return an evaluated integral in CAS. Don't know if this evaluated in previous firmware. Embarrassed to say that I don't know how to proceed integrating by parts...prime seems to want it in vector form. In any case, surprised that CAS doesn't work with this example. Home and plot handles it numerically with ease.
05-29-2014, 07:07 AM
Post: #4
 parisse Senior Member Posts: 1,300 Joined: Dec 2013
RE: Integral question
I'm fixing it (Xcas will be updated next week). It's not integration by part, it's recognition of a f(u)*u' pattern.
05-29-2014, 01:37 PM
Post: #5
 Tim Wessman Senior Member Posts: 2,292 Joined: Dec 2013
RE: Integral question
The last question as to why it doesn't spit out immediately a numerical result is due to the way the cas works. If something can't be evaluated symbolically (as bernard just pointed out in this case) it will return it unevaluated. Doing an approx(<returned_integral>) (the shift ENTER function) will return it as an approximate numerical result. Also, if you have 1. or similar as your limit at the bounds, it will automatically do it as an approximation immediately in 1 step since it has a "non-exact" number in the equation.

TW

Although I work for HP, the views and opinions I post here are my own.
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