Integration over the ellipsoid $M:={(x,y,z)mid x^2+frac{y^2}{4}+frac{z^2}{9}=1}$ using the divergence theorem...
$begingroup$
I have troubles with the following question:
Given is the following vector field :
$$f(x,y,z)= begin{pmatrix}x+sin(y)cos(z)\y+e^{x^2+y^2}\-z + log(1+x^2+y^2)end{pmatrix}$$
and the set $M$ is defined by
$$M:={(x,y,z)mid x^2+frac{y^2}{4}+frac{z^2}{9}=1}$$
Calculate the following integral :
$$int_Mlangle f, v rangle, dS$$
where $v$ is the unit normal field (german : Einheitsnormalenfeld) toward the exterior.
So I thought about using the divergence theorem as usual given that $M$ is just the border of an ellipsoid. I get the triple integral over $1+2ye^{x^2+y^2}$ . The 3 integrals over 1 give us the volume of a normal ellipsoid, in this case $8pi$, but how do I integrate $iiint_{text{Ellipsoid}} 2ye^{x^2+y^2} dx,dy,dz$ ?
Thanks for your help.
real-analysis integration
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add a comment |
$begingroup$
I have troubles with the following question:
Given is the following vector field :
$$f(x,y,z)= begin{pmatrix}x+sin(y)cos(z)\y+e^{x^2+y^2}\-z + log(1+x^2+y^2)end{pmatrix}$$
and the set $M$ is defined by
$$M:={(x,y,z)mid x^2+frac{y^2}{4}+frac{z^2}{9}=1}$$
Calculate the following integral :
$$int_Mlangle f, v rangle, dS$$
where $v$ is the unit normal field (german : Einheitsnormalenfeld) toward the exterior.
So I thought about using the divergence theorem as usual given that $M$ is just the border of an ellipsoid. I get the triple integral over $1+2ye^{x^2+y^2}$ . The 3 integrals over 1 give us the volume of a normal ellipsoid, in this case $8pi$, but how do I integrate $iiint_{text{Ellipsoid}} 2ye^{x^2+y^2} dx,dy,dz$ ?
Thanks for your help.
real-analysis integration
$endgroup$
add a comment |
$begingroup$
I have troubles with the following question:
Given is the following vector field :
$$f(x,y,z)= begin{pmatrix}x+sin(y)cos(z)\y+e^{x^2+y^2}\-z + log(1+x^2+y^2)end{pmatrix}$$
and the set $M$ is defined by
$$M:={(x,y,z)mid x^2+frac{y^2}{4}+frac{z^2}{9}=1}$$
Calculate the following integral :
$$int_Mlangle f, v rangle, dS$$
where $v$ is the unit normal field (german : Einheitsnormalenfeld) toward the exterior.
So I thought about using the divergence theorem as usual given that $M$ is just the border of an ellipsoid. I get the triple integral over $1+2ye^{x^2+y^2}$ . The 3 integrals over 1 give us the volume of a normal ellipsoid, in this case $8pi$, but how do I integrate $iiint_{text{Ellipsoid}} 2ye^{x^2+y^2} dx,dy,dz$ ?
Thanks for your help.
real-analysis integration
$endgroup$
I have troubles with the following question:
Given is the following vector field :
$$f(x,y,z)= begin{pmatrix}x+sin(y)cos(z)\y+e^{x^2+y^2}\-z + log(1+x^2+y^2)end{pmatrix}$$
and the set $M$ is defined by
$$M:={(x,y,z)mid x^2+frac{y^2}{4}+frac{z^2}{9}=1}$$
Calculate the following integral :
$$int_Mlangle f, v rangle, dS$$
where $v$ is the unit normal field (german : Einheitsnormalenfeld) toward the exterior.
So I thought about using the divergence theorem as usual given that $M$ is just the border of an ellipsoid. I get the triple integral over $1+2ye^{x^2+y^2}$ . The 3 integrals over 1 give us the volume of a normal ellipsoid, in this case $8pi$, but how do I integrate $iiint_{text{Ellipsoid}} 2ye^{x^2+y^2} dx,dy,dz$ ?
Thanks for your help.
real-analysis integration
real-analysis integration
edited Jan 7 at 19:33
Poujh
asked Jul 18 '18 at 19:18
PoujhPoujh
602516
602516
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1 Answer
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So you are asking how to set up a triple integral?
The ellipsoid $x^2+ frac{y^2}{4}+ frac{z^2}{9}= 1$ can be covered by taking $x$ from $-1$ to $1$; $y$, for each $x$, from $-2sqrt{1-x^2}$ to $2sqrt{1-x^2}$; and $z$, for each $x$ and $y$, from $-3sqrt{1-x^2-frac{y^2}{4}}$ to $3sqrt{1-x^2-frac{y^2}{4}}$.
So the integral will be $$int_{x=-1}^1int_{y=-2sqrt{1- x^2}}^{2sqrt{1- x^2}}int_{z=-3sqrt{1-x^2-frac{y^2}{4}}}^{3sqrt{1-x^2-frac{y^2}{4}}}left(1+ 2ye^{x^2+y^2}right)dz,dy,dx$$
Since the integrand is independent of $z$, the first integration gives
$$-6int_{x=-1}^1int_{y=-2sqrt{1- x^2}}^{2sqrt{1- x^2}}sqrt{1- x^2}left(1+ 2ye^{x^2+y^2}right)dy,dx$$
$endgroup$
1
$begingroup$
Thanks for your help, but isn't that really "complicated" ? I mean, the integral over 1 is easy, and the divergence of the vector field is also a lot easier than in "first" appearence, so do we really need to integrate $2ye^{x^2+y^2}$ in that way ? Isn't there a trick, or couldn't we for example use cylindrical/ spherical coordinates to make things easier ? I found this question in an old exam, and given that time in exam is often limited, the questions are generally not "that" hard, so I'm just a bit surprised.
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– Poujh
Jul 18 '18 at 19:42
1
$begingroup$
The first integral is an integral of an odd function over a symmetric interval, thus the entire calculation yields zero.
$endgroup$
– zokomoko
Jul 18 '18 at 20:07
add a comment |
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1 Answer
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1 Answer
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$begingroup$
So you are asking how to set up a triple integral?
The ellipsoid $x^2+ frac{y^2}{4}+ frac{z^2}{9}= 1$ can be covered by taking $x$ from $-1$ to $1$; $y$, for each $x$, from $-2sqrt{1-x^2}$ to $2sqrt{1-x^2}$; and $z$, for each $x$ and $y$, from $-3sqrt{1-x^2-frac{y^2}{4}}$ to $3sqrt{1-x^2-frac{y^2}{4}}$.
So the integral will be $$int_{x=-1}^1int_{y=-2sqrt{1- x^2}}^{2sqrt{1- x^2}}int_{z=-3sqrt{1-x^2-frac{y^2}{4}}}^{3sqrt{1-x^2-frac{y^2}{4}}}left(1+ 2ye^{x^2+y^2}right)dz,dy,dx$$
Since the integrand is independent of $z$, the first integration gives
$$-6int_{x=-1}^1int_{y=-2sqrt{1- x^2}}^{2sqrt{1- x^2}}sqrt{1- x^2}left(1+ 2ye^{x^2+y^2}right)dy,dx$$
$endgroup$
1
$begingroup$
Thanks for your help, but isn't that really "complicated" ? I mean, the integral over 1 is easy, and the divergence of the vector field is also a lot easier than in "first" appearence, so do we really need to integrate $2ye^{x^2+y^2}$ in that way ? Isn't there a trick, or couldn't we for example use cylindrical/ spherical coordinates to make things easier ? I found this question in an old exam, and given that time in exam is often limited, the questions are generally not "that" hard, so I'm just a bit surprised.
$endgroup$
– Poujh
Jul 18 '18 at 19:42
1
$begingroup$
The first integral is an integral of an odd function over a symmetric interval, thus the entire calculation yields zero.
$endgroup$
– zokomoko
Jul 18 '18 at 20:07
add a comment |
$begingroup$
So you are asking how to set up a triple integral?
The ellipsoid $x^2+ frac{y^2}{4}+ frac{z^2}{9}= 1$ can be covered by taking $x$ from $-1$ to $1$; $y$, for each $x$, from $-2sqrt{1-x^2}$ to $2sqrt{1-x^2}$; and $z$, for each $x$ and $y$, from $-3sqrt{1-x^2-frac{y^2}{4}}$ to $3sqrt{1-x^2-frac{y^2}{4}}$.
So the integral will be $$int_{x=-1}^1int_{y=-2sqrt{1- x^2}}^{2sqrt{1- x^2}}int_{z=-3sqrt{1-x^2-frac{y^2}{4}}}^{3sqrt{1-x^2-frac{y^2}{4}}}left(1+ 2ye^{x^2+y^2}right)dz,dy,dx$$
Since the integrand is independent of $z$, the first integration gives
$$-6int_{x=-1}^1int_{y=-2sqrt{1- x^2}}^{2sqrt{1- x^2}}sqrt{1- x^2}left(1+ 2ye^{x^2+y^2}right)dy,dx$$
$endgroup$
1
$begingroup$
Thanks for your help, but isn't that really "complicated" ? I mean, the integral over 1 is easy, and the divergence of the vector field is also a lot easier than in "first" appearence, so do we really need to integrate $2ye^{x^2+y^2}$ in that way ? Isn't there a trick, or couldn't we for example use cylindrical/ spherical coordinates to make things easier ? I found this question in an old exam, and given that time in exam is often limited, the questions are generally not "that" hard, so I'm just a bit surprised.
$endgroup$
– Poujh
Jul 18 '18 at 19:42
1
$begingroup$
The first integral is an integral of an odd function over a symmetric interval, thus the entire calculation yields zero.
$endgroup$
– zokomoko
Jul 18 '18 at 20:07
add a comment |
$begingroup$
So you are asking how to set up a triple integral?
The ellipsoid $x^2+ frac{y^2}{4}+ frac{z^2}{9}= 1$ can be covered by taking $x$ from $-1$ to $1$; $y$, for each $x$, from $-2sqrt{1-x^2}$ to $2sqrt{1-x^2}$; and $z$, for each $x$ and $y$, from $-3sqrt{1-x^2-frac{y^2}{4}}$ to $3sqrt{1-x^2-frac{y^2}{4}}$.
So the integral will be $$int_{x=-1}^1int_{y=-2sqrt{1- x^2}}^{2sqrt{1- x^2}}int_{z=-3sqrt{1-x^2-frac{y^2}{4}}}^{3sqrt{1-x^2-frac{y^2}{4}}}left(1+ 2ye^{x^2+y^2}right)dz,dy,dx$$
Since the integrand is independent of $z$, the first integration gives
$$-6int_{x=-1}^1int_{y=-2sqrt{1- x^2}}^{2sqrt{1- x^2}}sqrt{1- x^2}left(1+ 2ye^{x^2+y^2}right)dy,dx$$
$endgroup$
So you are asking how to set up a triple integral?
The ellipsoid $x^2+ frac{y^2}{4}+ frac{z^2}{9}= 1$ can be covered by taking $x$ from $-1$ to $1$; $y$, for each $x$, from $-2sqrt{1-x^2}$ to $2sqrt{1-x^2}$; and $z$, for each $x$ and $y$, from $-3sqrt{1-x^2-frac{y^2}{4}}$ to $3sqrt{1-x^2-frac{y^2}{4}}$.
So the integral will be $$int_{x=-1}^1int_{y=-2sqrt{1- x^2}}^{2sqrt{1- x^2}}int_{z=-3sqrt{1-x^2-frac{y^2}{4}}}^{3sqrt{1-x^2-frac{y^2}{4}}}left(1+ 2ye^{x^2+y^2}right)dz,dy,dx$$
Since the integrand is independent of $z$, the first integration gives
$$-6int_{x=-1}^1int_{y=-2sqrt{1- x^2}}^{2sqrt{1- x^2}}sqrt{1- x^2}left(1+ 2ye^{x^2+y^2}right)dy,dx$$
edited Jul 18 '18 at 20:02
Robert Howard
1,9161822
1,9161822
answered Jul 18 '18 at 19:36
user247327user247327
10.6k1515
10.6k1515
1
$begingroup$
Thanks for your help, but isn't that really "complicated" ? I mean, the integral over 1 is easy, and the divergence of the vector field is also a lot easier than in "first" appearence, so do we really need to integrate $2ye^{x^2+y^2}$ in that way ? Isn't there a trick, or couldn't we for example use cylindrical/ spherical coordinates to make things easier ? I found this question in an old exam, and given that time in exam is often limited, the questions are generally not "that" hard, so I'm just a bit surprised.
$endgroup$
– Poujh
Jul 18 '18 at 19:42
1
$begingroup$
The first integral is an integral of an odd function over a symmetric interval, thus the entire calculation yields zero.
$endgroup$
– zokomoko
Jul 18 '18 at 20:07
add a comment |
1
$begingroup$
Thanks for your help, but isn't that really "complicated" ? I mean, the integral over 1 is easy, and the divergence of the vector field is also a lot easier than in "first" appearence, so do we really need to integrate $2ye^{x^2+y^2}$ in that way ? Isn't there a trick, or couldn't we for example use cylindrical/ spherical coordinates to make things easier ? I found this question in an old exam, and given that time in exam is often limited, the questions are generally not "that" hard, so I'm just a bit surprised.
$endgroup$
– Poujh
Jul 18 '18 at 19:42
1
$begingroup$
The first integral is an integral of an odd function over a symmetric interval, thus the entire calculation yields zero.
$endgroup$
– zokomoko
Jul 18 '18 at 20:07
1
1
$begingroup$
Thanks for your help, but isn't that really "complicated" ? I mean, the integral over 1 is easy, and the divergence of the vector field is also a lot easier than in "first" appearence, so do we really need to integrate $2ye^{x^2+y^2}$ in that way ? Isn't there a trick, or couldn't we for example use cylindrical/ spherical coordinates to make things easier ? I found this question in an old exam, and given that time in exam is often limited, the questions are generally not "that" hard, so I'm just a bit surprised.
$endgroup$
– Poujh
Jul 18 '18 at 19:42
$begingroup$
Thanks for your help, but isn't that really "complicated" ? I mean, the integral over 1 is easy, and the divergence of the vector field is also a lot easier than in "first" appearence, so do we really need to integrate $2ye^{x^2+y^2}$ in that way ? Isn't there a trick, or couldn't we for example use cylindrical/ spherical coordinates to make things easier ? I found this question in an old exam, and given that time in exam is often limited, the questions are generally not "that" hard, so I'm just a bit surprised.
$endgroup$
– Poujh
Jul 18 '18 at 19:42
1
1
$begingroup$
The first integral is an integral of an odd function over a symmetric interval, thus the entire calculation yields zero.
$endgroup$
– zokomoko
Jul 18 '18 at 20:07
$begingroup$
The first integral is an integral of an odd function over a symmetric interval, thus the entire calculation yields zero.
$endgroup$
– zokomoko
Jul 18 '18 at 20:07
add a comment |
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