Integration

[Helge Gabert]

I ran across this simple definite integral recently

int(x,x,0,3) and the Prime hangs. I tried other limits and no problems.

[DrD]

I just tried your simple, definite integral int(x,x,0,3), with emulator in cas view;
in this case, the only thing hung was a nine over a two.

[Helge Gabert]

I'm using the physical Prime.

I tried the emulator as well, and if you pay close attention, you will notice a certain lag with this problem. Subsitute other limits, and the response is instantaneous. Go figure.

[Terje Vallestad]

(04-03-2014 05:01 PM)Helge Gabert Wrote:  I'm using the physical Prime.

I tried the emulator as well, and if you pay close attention, you will notice a certain lag with this problem. Subsitute other limits, and the response is instantaneous. Go figure.

Using the physical Prime.

If you uncheck the Exact flag in CAS, you get the message:
Adaptive method failure, will try with Romberg, last approximation was 4.5

If you leave the flag set and hit "On" after starting the calculation you get 9/2 instantly.

In Home if you use the Template and input the integral, the calc hangs and pressing On results in
Error: Invalid input, but only if the CAS a Exact flag is set. With the flag clear you get 4.5.

Very strange

Cheers, Terje

[orcinus]

It doesn't really "hang".

It takes its sweet time, during which there's an animated hourglass in the top right corner of the screen, indicating activity. After a while, it spits out 9/2.

While on the subject, is there a way to interrupt/cancel a calculation?

[Helge Gabert]

Yes, cancel with Esc or ON. Or ON-Symb if ESC or ON don't work.

By the way, the above integral can be computed immediately by hitting the ON key, after pressing ENTER.

[orcinus]

(04-04-2014 01:38 AM)Helge Gabert Wrote:  By the way, the above integral can be computed immediately by hitting the ON key, after pressing ENTER.

Now *that* is truly bizarre. So it gets the result immediately, but... Decides to pretend it's taking longer?

Quote:James T. Kirk: Mr. Scott. Have you always multiplied your repair estimates by a factor of four?
Montgomery Scott: Certainly, Sir. How else can I keep my reputation as a miracle worker?

[Helge Gabert]

Yes, bizarre is the word.

Also, why would other integration limits not present any lag time problems, e.g., int(x,x,-3,0) or int(x,x,0,5) are fine, only integrating x dx between 0 and 3 exhibits this behavior?

[Helge Gabert]

FWIW, further analysis shows that this behavior is affected by an upper limit of the form 3*2^(n-1), n=1,2,. . . , i.e., 3, 6, 12, 24, . . . , with a lower limit of 0.