Triple Integrals Problem
12-12-2014, 06:14 AM
Post: #1
 marcusnicolas1 Junior Member Posts: 39 Joined: Dec 2014
Triple Integrals Problem
So I did a triple integral in the non cas mode. It gave me the exact number in decimal form instead of giving me 96pi. However when I try to do the same operation in the CAS mode, it gives me an error. But when I reduce the integral to a single integral it gives me the correct answer. I am not sure what I am doing wrong. Can anyone help me with this please? Thanks
12-12-2014, 11:17 AM
Post: #2
 Gilles Member Posts: 225 Joined: Oct 2014
RE: Triple Integrals Problem
(12-12-2014 06:14 AM)marcusnicolas1 Wrote:  So I did a triple integral in the non cas mode. It gave me the exact number in decimal form instead of giving me 96pi. However when I try to do the same operation in the CAS mode, it gives me an error. But when I reduce the integral to a single integral it gives me the correct answer. I am not sure what I am doing wrong. Can anyone help me with this please? Thanks

Can you post your triple integral ?
12-18-2014, 09:41 PM
Post: #3
 marcusnicolas1 Junior Member Posts: 39 Joined: Dec 2014
RE: Triple Integrals Problem
How do I post the integral?
12-18-2014, 09:53 PM (This post was last modified: 12-18-2014 10:29 PM by Snorre.)
Post: #4
 Snorre Member Posts: 101 Joined: Dec 2013
RE: Triple Integrals Problem
(12-18-2014 09:41 PM)marcusnicolas1 Wrote:  How do I post the integral?

1. Either as text: int(int(int(f(x,y,z),x=a..b),y=c..d),z=g..h)
2. Or as image: enter it in emulator, make a screenshot by selecting >[copy screen] from the window's menu bar, save it to desktop, and upload it as an attachment to your post
3. Or the TeXy way: enter it as TeX-like code into your post (haven't tried it yet)
4. Or the creative way: write it down on a piece of paper, make a photo (scale this down to a reasonable size) und upload it as an attachment
12-18-2014, 10:12 PM
Post: #5
 marcusnicolas1 Junior Member Posts: 39 Joined: Dec 2014
RE: Triple Integrals Problem
I use the actual symbol but here is basically what I do ..... int(int(int(r,z,0,r^2 -4)1,r,2,3)1,x,0,2pi) .... this is supposed to produce (25pi)/2. It does not work. I get error messages. I am thinking it is the way I put it together but I can not figure it out. I had another problem to use but I can not remember what it is.
12-18-2014, 10:44 PM (This post was last modified: 12-18-2014 11:17 PM by Snorre.)
Post: #6
 Snorre Member Posts: 101 Joined: Dec 2013
RE: Triple Integrals Problem
Hello,

I'm not sure if I got it right, but did you mean that:

(I've put parentheses in the first screenshot while entering for better readability; these were automagically gone after evaluating in the second screenshot.)
This seems to give the expected result (after printing out a warning -- ignore that for now).

To enter this, either use the integral template by pressing the template key (where the orange letter C is printed on) and fill out the "holes" until it looks right.

Or -- easier to describe here -- enter:
Code:
int(int(int(r,z=0..r²-4),r=2..3),x=0..2*π)
(BTW: I prefer the ".." notation for integration limits as this is easier to parse for my tired eyes).

P.S. you needn't to keep two threads about the same question alive.
12-19-2014, 02:29 AM
Post: #7
 marcusnicolas1 Junior Member Posts: 39 Joined: Dec 2014
RE: Triple Integrals Problem
When I do use the "C" button to get to the integrand symbol, it gives it to me however it seems as though it is on one line. I do not see where I can fill in the spaces with what I need. I get something that looks like "integral sign" then () .... From there I thought I have to put in Open bracket .... the function then comma, with respect to ... comma, then from lower limit .... comma, then to lower limit ... closed bracket. Mine does not look like the setup you had
12-19-2014, 02:30 AM
Post: #8
 marcusnicolas1 Junior Member Posts: 39 Joined: Dec 2014
RE: Triple Integrals Problem
I want to be able to fill in the holes. I do not seem to have that option
12-19-2014, 03:06 AM
Post: #9
 marcusnicolas1 Junior Member Posts: 39 Joined: Dec 2014
RE: Triple Integrals Problem
OK ... it works beautifully now. My firmware was not updated. Once I plugged it into my laptop, it updated and I can use it just like you did it. Thanks for your help.
12-19-2014, 09:40 AM
Post: #10
 Snorre Member Posts: 101 Joined: Dec 2013
RE: Triple Integrals Problem
Hi,
I think your "Entry" setting was "Algebraic". By updating the firmware it was set back to the default "Textbook". You will find it at [Shift]>[Home Settings]>"Entry".
Greetings
12-20-2014, 01:09 AM
Post: #11
 marcusnicolas1 Junior Member Posts: 39 Joined: Dec 2014
RE: Triple Integrals Problem
So should I reset it to algebraic or leave it as is
12-20-2014, 01:14 AM
Post: #12
 marcusnicolas1 Junior Member Posts: 39 Joined: Dec 2014
RE: Triple Integrals Problem
Also, is there a way to graph a sphere on the Prime?
12-20-2014, 03:53 PM
Post: #13
 Snorre Member Posts: 101 Joined: Dec 2013
RE: Triple Integrals Problem
(12-20-2014 01:09 AM)marcusnicolas1 Wrote:  So should I reset it to algebraic or leave it as is

This only affects how expressions are entered and displayed, so set it to your preference.

Quote:Also, is there a way to graph a sphere on the Prime?

Take a look at Han's Graph3D app.
12-24-2014, 03:59 AM
Post: #14
 marcusnicolas1 Junior Member Posts: 39 Joined: Dec 2014
RE: Triple Integrals Problem
I downloaded the Graph3D 2.42 version. It seems as though I can not longer plot the function of square root of -X^2 -Y^2, It gives me a box with nothing inside of it. Also, I have been trying to plot a sphere and can not do so. I know a sphere is X^2 + Y^2 +Z^2 equals a number. However I can not seem to plot that. Can anyone help me with this please? THank you.
12-24-2014, 08:27 AM
Post: #15
 Snorre Member Posts: 101 Joined: Dec 2013
RE: Triple Integrals Problem
(12-24-2014 03:59 AM)marcusnicolas1 Wrote:  I downloaded the Graph3D 2.42 version. It seems as though I can not longer plot the function of square root of -X^2 -Y^2, It gives me a box with nothing inside of it. Also, I have been trying to plot a sphere and can not do so. I know a sphere is X^2 + Y^2 +Z^2 equals a number. However I can not seem to plot that. Can anyone help me with this please? THank you.

Hello,

You're on the right path. As you've noticed a sphere can be definied by x²+y²+z²=r², so z=±√(r²-x²-y²).
In your first attempt you omitted the radius, which means you were plotting a sphere with radius r=0.
Just try again by first setting R:=10, then plotting √(R²-X²-Y²), and also -√(R²-X²-Y²).
12-31-2014, 07:31 AM
Post: #16
 marcusnicolas1 Junior Member Posts: 39 Joined: Dec 2014
RE: Triple Integrals Problem
Thank you for your help.
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