how to find the limits for this type of integrals using spherical coordinates
$begingroup$
move the integral
$int_0^1 int_0^{sqrt{1 - x^2}} int_0^{sqrt{1 - x^2 - y^2}} sqrt{x^2 + y^2 + z^2},mathrm dz,mathrm dy,mathrm dx = frac{pi}{8}$
to spherical coordinates integral.
i dont know how to find the limits of the integral when moving to $theta, r , phi $
can you please guide me with finding the limits because i always get a mistakes there
my trial :
reading the $mathrm dz$ we see that $ 0 leq z^2 leq 1-x^2-y^2 $
or $ 0leq x^2 + y^2 + z^2 leq 1 $
reading $mathrm dy$ we see that $ 0 leq y^2 leq sqrt{1-x^2} $ or $ 0leq x^2 + y^2 leq 1$
reading $dx$ we see that $ 0 leq x leq 1$
so the spherical limits :
$ 0leq r^2 leq 1$
$ 0 leq r^2sin(theta)^2 leq 1$
$ 0 leq rcos(theta)sin(phi) leq 1$
how do i continue from here ? i think i made a mistake with $phi$ because i didn't get the proper value for the integral after calculating in the spherical co-ordinates.
integration multivariable-calculus spherical-coordinates jacobian
$endgroup$
add a comment |
$begingroup$
move the integral
$int_0^1 int_0^{sqrt{1 - x^2}} int_0^{sqrt{1 - x^2 - y^2}} sqrt{x^2 + y^2 + z^2},mathrm dz,mathrm dy,mathrm dx = frac{pi}{8}$
to spherical coordinates integral.
i dont know how to find the limits of the integral when moving to $theta, r , phi $
can you please guide me with finding the limits because i always get a mistakes there
my trial :
reading the $mathrm dz$ we see that $ 0 leq z^2 leq 1-x^2-y^2 $
or $ 0leq x^2 + y^2 + z^2 leq 1 $
reading $mathrm dy$ we see that $ 0 leq y^2 leq sqrt{1-x^2} $ or $ 0leq x^2 + y^2 leq 1$
reading $dx$ we see that $ 0 leq x leq 1$
so the spherical limits :
$ 0leq r^2 leq 1$
$ 0 leq r^2sin(theta)^2 leq 1$
$ 0 leq rcos(theta)sin(phi) leq 1$
how do i continue from here ? i think i made a mistake with $phi$ because i didn't get the proper value for the integral after calculating in the spherical co-ordinates.
integration multivariable-calculus spherical-coordinates jacobian
$endgroup$
1
$begingroup$
You lost the point that $x,y,z$ are all positive
$endgroup$
– Damien
Dec 25 '18 at 11:20
add a comment |
$begingroup$
move the integral
$int_0^1 int_0^{sqrt{1 - x^2}} int_0^{sqrt{1 - x^2 - y^2}} sqrt{x^2 + y^2 + z^2},mathrm dz,mathrm dy,mathrm dx = frac{pi}{8}$
to spherical coordinates integral.
i dont know how to find the limits of the integral when moving to $theta, r , phi $
can you please guide me with finding the limits because i always get a mistakes there
my trial :
reading the $mathrm dz$ we see that $ 0 leq z^2 leq 1-x^2-y^2 $
or $ 0leq x^2 + y^2 + z^2 leq 1 $
reading $mathrm dy$ we see that $ 0 leq y^2 leq sqrt{1-x^2} $ or $ 0leq x^2 + y^2 leq 1$
reading $dx$ we see that $ 0 leq x leq 1$
so the spherical limits :
$ 0leq r^2 leq 1$
$ 0 leq r^2sin(theta)^2 leq 1$
$ 0 leq rcos(theta)sin(phi) leq 1$
how do i continue from here ? i think i made a mistake with $phi$ because i didn't get the proper value for the integral after calculating in the spherical co-ordinates.
integration multivariable-calculus spherical-coordinates jacobian
$endgroup$
move the integral
$int_0^1 int_0^{sqrt{1 - x^2}} int_0^{sqrt{1 - x^2 - y^2}} sqrt{x^2 + y^2 + z^2},mathrm dz,mathrm dy,mathrm dx = frac{pi}{8}$
to spherical coordinates integral.
i dont know how to find the limits of the integral when moving to $theta, r , phi $
can you please guide me with finding the limits because i always get a mistakes there
my trial :
reading the $mathrm dz$ we see that $ 0 leq z^2 leq 1-x^2-y^2 $
or $ 0leq x^2 + y^2 + z^2 leq 1 $
reading $mathrm dy$ we see that $ 0 leq y^2 leq sqrt{1-x^2} $ or $ 0leq x^2 + y^2 leq 1$
reading $dx$ we see that $ 0 leq x leq 1$
so the spherical limits :
$ 0leq r^2 leq 1$
$ 0 leq r^2sin(theta)^2 leq 1$
$ 0 leq rcos(theta)sin(phi) leq 1$
how do i continue from here ? i think i made a mistake with $phi$ because i didn't get the proper value for the integral after calculating in the spherical co-ordinates.
integration multivariable-calculus spherical-coordinates jacobian
integration multivariable-calculus spherical-coordinates jacobian
edited Dec 25 '18 at 11:44
José Carlos Santos
173k23133241
173k23133241
asked Dec 25 '18 at 10:51
Mather Mather
4028
4028
1
$begingroup$
You lost the point that $x,y,z$ are all positive
$endgroup$
– Damien
Dec 25 '18 at 11:20
add a comment |
1
$begingroup$
You lost the point that $x,y,z$ are all positive
$endgroup$
– Damien
Dec 25 '18 at 11:20
1
1
$begingroup$
You lost the point that $x,y,z$ are all positive
$endgroup$
– Damien
Dec 25 '18 at 11:20
$begingroup$
You lost the point that $x,y,z$ are all positive
$endgroup$
– Damien
Dec 25 '18 at 11:20
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
It follows from your computations that your integral is equal to$$int_0^1int_0^{fracpi2}int_0^{fracpi2}r^3sin(phi),mathrm dtheta,mathrm dphi,mathrm dr.$$Butbegin{align}int_0^1int_0^{fracpi2}int_0^{fracpi2}r^3sin(phi),mathrm dtheta,mathrm dphi,mathrm dr&=left(int_0^1r^3,mathrm drright)left(int_0^{fracpi2}sin(phi),mathrm dphiright)left(int_0^{fracpi2},mathrm dthetaright)\&=frac14times1timesfracpi2\&=fracpi8.end{align}
$endgroup$
$begingroup$
how did you know that $ 0 leq theta leq frac{pi}{2} $
$endgroup$
– Mather
Dec 25 '18 at 11:36
$begingroup$
Because $x,y,zleqslant0$.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:38
$begingroup$
also why is $ 0leq r leq 1 $ and not $ 0leq r leq frac{1}{sin{theta} }$
$endgroup$
– Mather
Dec 25 '18 at 11:38
$begingroup$
Why should we have that? The region that you are interested in is the part of the unit sphere in which all Cartesian coordinates are non-negative. So, $r$ can take any value from $0$ to $1$, whatever $theta$ may be.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:42
$begingroup$
yes but the inequality says (by moving from xyz , to spherical ) that $ 0 leq r^2sin(theta)^2 leq 1 $ so dividing makes the ineuality $(a)$ $ 0leq r leq frac{1}{sin(theta)} $ doesn't it ?
$endgroup$
– Mather
Dec 25 '18 at 11:46
|
show 1 more comment
Your Answer
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1 Answer
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oldest
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1 Answer
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$begingroup$
It follows from your computations that your integral is equal to$$int_0^1int_0^{fracpi2}int_0^{fracpi2}r^3sin(phi),mathrm dtheta,mathrm dphi,mathrm dr.$$Butbegin{align}int_0^1int_0^{fracpi2}int_0^{fracpi2}r^3sin(phi),mathrm dtheta,mathrm dphi,mathrm dr&=left(int_0^1r^3,mathrm drright)left(int_0^{fracpi2}sin(phi),mathrm dphiright)left(int_0^{fracpi2},mathrm dthetaright)\&=frac14times1timesfracpi2\&=fracpi8.end{align}
$endgroup$
$begingroup$
how did you know that $ 0 leq theta leq frac{pi}{2} $
$endgroup$
– Mather
Dec 25 '18 at 11:36
$begingroup$
Because $x,y,zleqslant0$.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:38
$begingroup$
also why is $ 0leq r leq 1 $ and not $ 0leq r leq frac{1}{sin{theta} }$
$endgroup$
– Mather
Dec 25 '18 at 11:38
$begingroup$
Why should we have that? The region that you are interested in is the part of the unit sphere in which all Cartesian coordinates are non-negative. So, $r$ can take any value from $0$ to $1$, whatever $theta$ may be.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:42
$begingroup$
yes but the inequality says (by moving from xyz , to spherical ) that $ 0 leq r^2sin(theta)^2 leq 1 $ so dividing makes the ineuality $(a)$ $ 0leq r leq frac{1}{sin(theta)} $ doesn't it ?
$endgroup$
– Mather
Dec 25 '18 at 11:46
|
show 1 more comment
$begingroup$
It follows from your computations that your integral is equal to$$int_0^1int_0^{fracpi2}int_0^{fracpi2}r^3sin(phi),mathrm dtheta,mathrm dphi,mathrm dr.$$Butbegin{align}int_0^1int_0^{fracpi2}int_0^{fracpi2}r^3sin(phi),mathrm dtheta,mathrm dphi,mathrm dr&=left(int_0^1r^3,mathrm drright)left(int_0^{fracpi2}sin(phi),mathrm dphiright)left(int_0^{fracpi2},mathrm dthetaright)\&=frac14times1timesfracpi2\&=fracpi8.end{align}
$endgroup$
$begingroup$
how did you know that $ 0 leq theta leq frac{pi}{2} $
$endgroup$
– Mather
Dec 25 '18 at 11:36
$begingroup$
Because $x,y,zleqslant0$.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:38
$begingroup$
also why is $ 0leq r leq 1 $ and not $ 0leq r leq frac{1}{sin{theta} }$
$endgroup$
– Mather
Dec 25 '18 at 11:38
$begingroup$
Why should we have that? The region that you are interested in is the part of the unit sphere in which all Cartesian coordinates are non-negative. So, $r$ can take any value from $0$ to $1$, whatever $theta$ may be.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:42
$begingroup$
yes but the inequality says (by moving from xyz , to spherical ) that $ 0 leq r^2sin(theta)^2 leq 1 $ so dividing makes the ineuality $(a)$ $ 0leq r leq frac{1}{sin(theta)} $ doesn't it ?
$endgroup$
– Mather
Dec 25 '18 at 11:46
|
show 1 more comment
$begingroup$
It follows from your computations that your integral is equal to$$int_0^1int_0^{fracpi2}int_0^{fracpi2}r^3sin(phi),mathrm dtheta,mathrm dphi,mathrm dr.$$Butbegin{align}int_0^1int_0^{fracpi2}int_0^{fracpi2}r^3sin(phi),mathrm dtheta,mathrm dphi,mathrm dr&=left(int_0^1r^3,mathrm drright)left(int_0^{fracpi2}sin(phi),mathrm dphiright)left(int_0^{fracpi2},mathrm dthetaright)\&=frac14times1timesfracpi2\&=fracpi8.end{align}
$endgroup$
It follows from your computations that your integral is equal to$$int_0^1int_0^{fracpi2}int_0^{fracpi2}r^3sin(phi),mathrm dtheta,mathrm dphi,mathrm dr.$$Butbegin{align}int_0^1int_0^{fracpi2}int_0^{fracpi2}r^3sin(phi),mathrm dtheta,mathrm dphi,mathrm dr&=left(int_0^1r^3,mathrm drright)left(int_0^{fracpi2}sin(phi),mathrm dphiright)left(int_0^{fracpi2},mathrm dthetaright)\&=frac14times1timesfracpi2\&=fracpi8.end{align}
answered Dec 25 '18 at 11:34
José Carlos SantosJosé Carlos Santos
173k23133241
173k23133241
$begingroup$
how did you know that $ 0 leq theta leq frac{pi}{2} $
$endgroup$
– Mather
Dec 25 '18 at 11:36
$begingroup$
Because $x,y,zleqslant0$.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:38
$begingroup$
also why is $ 0leq r leq 1 $ and not $ 0leq r leq frac{1}{sin{theta} }$
$endgroup$
– Mather
Dec 25 '18 at 11:38
$begingroup$
Why should we have that? The region that you are interested in is the part of the unit sphere in which all Cartesian coordinates are non-negative. So, $r$ can take any value from $0$ to $1$, whatever $theta$ may be.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:42
$begingroup$
yes but the inequality says (by moving from xyz , to spherical ) that $ 0 leq r^2sin(theta)^2 leq 1 $ so dividing makes the ineuality $(a)$ $ 0leq r leq frac{1}{sin(theta)} $ doesn't it ?
$endgroup$
– Mather
Dec 25 '18 at 11:46
|
show 1 more comment
$begingroup$
how did you know that $ 0 leq theta leq frac{pi}{2} $
$endgroup$
– Mather
Dec 25 '18 at 11:36
$begingroup$
Because $x,y,zleqslant0$.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:38
$begingroup$
also why is $ 0leq r leq 1 $ and not $ 0leq r leq frac{1}{sin{theta} }$
$endgroup$
– Mather
Dec 25 '18 at 11:38
$begingroup$
Why should we have that? The region that you are interested in is the part of the unit sphere in which all Cartesian coordinates are non-negative. So, $r$ can take any value from $0$ to $1$, whatever $theta$ may be.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:42
$begingroup$
yes but the inequality says (by moving from xyz , to spherical ) that $ 0 leq r^2sin(theta)^2 leq 1 $ so dividing makes the ineuality $(a)$ $ 0leq r leq frac{1}{sin(theta)} $ doesn't it ?
$endgroup$
– Mather
Dec 25 '18 at 11:46
$begingroup$
how did you know that $ 0 leq theta leq frac{pi}{2} $
$endgroup$
– Mather
Dec 25 '18 at 11:36
$begingroup$
how did you know that $ 0 leq theta leq frac{pi}{2} $
$endgroup$
– Mather
Dec 25 '18 at 11:36
$begingroup$
Because $x,y,zleqslant0$.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:38
$begingroup$
Because $x,y,zleqslant0$.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:38
$begingroup$
also why is $ 0leq r leq 1 $ and not $ 0leq r leq frac{1}{sin{theta} }$
$endgroup$
– Mather
Dec 25 '18 at 11:38
$begingroup$
also why is $ 0leq r leq 1 $ and not $ 0leq r leq frac{1}{sin{theta} }$
$endgroup$
– Mather
Dec 25 '18 at 11:38
$begingroup$
Why should we have that? The region that you are interested in is the part of the unit sphere in which all Cartesian coordinates are non-negative. So, $r$ can take any value from $0$ to $1$, whatever $theta$ may be.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:42
$begingroup$
Why should we have that? The region that you are interested in is the part of the unit sphere in which all Cartesian coordinates are non-negative. So, $r$ can take any value from $0$ to $1$, whatever $theta$ may be.
$endgroup$
– José Carlos Santos
Dec 25 '18 at 11:42
$begingroup$
yes but the inequality says (by moving from xyz , to spherical ) that $ 0 leq r^2sin(theta)^2 leq 1 $ so dividing makes the ineuality $(a)$ $ 0leq r leq frac{1}{sin(theta)} $ doesn't it ?
$endgroup$
– Mather
Dec 25 '18 at 11:46
$begingroup$
yes but the inequality says (by moving from xyz , to spherical ) that $ 0 leq r^2sin(theta)^2 leq 1 $ so dividing makes the ineuality $(a)$ $ 0leq r leq frac{1}{sin(theta)} $ doesn't it ?
$endgroup$
– Mather
Dec 25 '18 at 11:46
|
show 1 more comment
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$begingroup$
You lost the point that $x,y,z$ are all positive
$endgroup$
– Damien
Dec 25 '18 at 11:20