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surface area question
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On Thu, 10 Jan 2008 06:14:03 -0800 (PST), Casper <...@gmail.com> wrote:
here is the question
i will type the maple command as expresstions
Int(2*Pi*y*sqrt(1+(Diff(y(x),x))^2),x);
Int(2*Pi*abs(y)*sqrt(1+(Diff(y(x),x))^2),x);
personally i think the 2nd one is correct.
however i serached many resources on the web, there is no abs sign....
it's just say
y:=x->-6;
int(2*Pi*y(x)*sqrt(1+(diff(y(x),x))^2),x=1..6);
it returens -60*Pi , which is definitely wrong.
on the other hand
int(2*Pi*abs(y(x))*sqrt(1+(diff(y(x),x))^2),x=1..6);
60*Pi
that should be the correct answer
what are your views?
thanks!
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On Thu, 10 Jan 2008 06:16:02 -0800 (PST), Casper <...@gmail.com> wrote:
On 10 Jan, 14:14, Casper <...@gmail.com> wrote:
> here is the question
>
> i will type the maple command as expresstions
>
> Int(2*Pi*y*sqrt(1+(Diff(y(x),x))^2),x);
>
> Int(2*Pi*abs(y)*sqrt(1+(Diff(y(x),x))^2),x);
>
> personally i think the 2nd one is correct.
>
> however i serached many resources on the web, there is no abs sign....
>
> it's just say
>
> y:=x->-6;
>
> int(2*Pi*y(x)*sqrt(1+(diff(y(x),x))^2),x=1..6);
>
> it returens -60*Pi , which is definitely wrong.
>
> on the other hand
>
> int(2*Pi*abs(y(x))*sqrt(1+(diff(y(x),x))^2),x=1..6);
>
> 60*Pi
>
> that should be the correct answer
>
> what are your views?
>
> thanks!
SORRY
surface area:
i meant the surface area by rotating the function about the x-axis!
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On Thu, 10 Jan 2008 09:28:08 -0500, A N Niel <...@nym.alias.net.invalid> wrote:
In article
<...@i12g2000prf.googlegroups.com>,
Casper <...@gmail.com> wrote:
> here is the question
>
>
> i will type the maple command as expresstions
>
> Int(2*Pi*y*sqrt(1+(Diff(y(x),x))^2),x);
>
>
> Int(2*Pi*abs(y)*sqrt(1+(Diff(y(x),x))^2),x);
>
> personally i think the 2nd one is correct.
>
>
> however i serached many resources on the web, there is no abs sign....
>
I looked in a textbook, and one of the conditions there was
[in your notation] y(x) > 0
>
>
> it's just say
>
> y:=x->-6;
>
>
> int(2*Pi*y(x)*sqrt(1+(diff(y(x),x))^2),x=1..6);
>
> it returens -60*Pi , which is definitely wrong.
>
> on the other hand
>
> int(2*Pi*abs(y(x))*sqrt(1+(diff(y(x),x))^2),x=1..6);
>
> 60*Pi
>
>
> that should be the correct answer
>
>
> what are your views?
>
> thanks!
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On Thu, 10 Jan 2008 17:08:11 -0800 (PST), Casper <...@gmail.com> wrote:
On 10 Jan, 14:28, A N Niel <...@nym.alias.net.invalid> wrote:
> In article
> <...@i12g2000prf.googlegroups.com>,
>
>
>
> Casper <...@gmail.com> wrote:
> > here is the question
>
> > i will type the maple command as expresstions
>
> > Int(2*Pi*y*sqrt(1+(Diff(y(x),x))^2),x);
>
> > Int(2*Pi*abs(y)*sqrt(1+(Diff(y(x),x))^2),x);
>
> > personally i think the 2nd one is correct.
>
> > however i serached many resources on the web, there is no abs sign....
>
> I looked in a textbook, and one of the conditions there was
> [in your notation] y(x) > 0
>
>
>
> > it's just say
>
> > y:=x->-6;
>
> > int(2*Pi*y(x)*sqrt(1+(diff(y(x),x))^2),x=1..6);
>
> > it returens -60*Pi , which is definitely wrong.
>
> > on the other hand
>
> > int(2*Pi*abs(y(x))*sqrt(1+(diff(y(x),x))^2),x=1..6);
>
> > 60*Pi
>
> > that should be the correct answer
>
> > what are your views?
>
> > thanks!
so if it dose not specify, it should have an abs sign..
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