How do I change $\int_{0}^{1}{\int_{0}^{\sqrt{1-{{x}^{2}}}}{\int_{\sqrt{{{x}^{2}}+{{y}^{2}}}}^{\sqrt{2-{{x}^{2}}-{{y}^{2}}}}{xydzdydx}}}$ to cylindrical or spherical coordinates?
Answer
615.3k+ views
Hint: In this question, we have to convert the given definite integral into cylindrical coordinates or the spherical coordinates. Thus, we start our problem by solving the limit z of the given integral. After that, we will find the value of $\rho $ from the second limit of the z. After that, we will find the value of z by substituting the value of the first limit of z in the second limit of z. Then, we will make the necessary calculations and then we will find the value of $\phi $ and $\theta $ from the conversion of z and from the equation of sphere. In the end, we will put the new limits in the integral and the x, y conversions, to get the required result for the problem.
Complete step-by-step solution:
According to the problem, we have to find the cylindrical or spherical coordinates from a definite integral.
Thus, we will apply the polar form to get the solution.
The integral given to us is $\int_{0}^{1}{\int_{0}^{\sqrt{1-{{x}^{2}}}}{\int_{\sqrt{{{x}^{2}}+{{y}^{2}}}}^{\sqrt{2-{{x}^{2}}-{{y}^{2}}}}{xydzdydx}}}$ --------- (1)
So, from equation (1), we get the value of the limit equals to
$\sqrt{{{x}^{2}}+{{y}^{2}}}\le z\le \sqrt{2-{{x}^{2}}-{{y}^{2}}}$
$0\le y\le \sqrt{1-{{x}^{2}}}$
$0\le x\le 1$
Now, we will first solve the z-domain, that is
$z=\sqrt{{{x}^{2}}+{{y}^{2}}}$ ------- (2) and
$z=\sqrt{2-{{x}^{2}}-{{y}^{2}}}$ ---------- (3)
Now, we will solve equation (2), which is
$z=\sqrt{{{x}^{2}}+{{y}^{2}}}$
So, we will square both sides in the above equation, we get
$\Rightarrow {{z}^{2}}={{\left( \sqrt{{{x}^{2}}+{{y}^{2}}} \right)}^{2}}$
On further solving the above problem, we get
$\Rightarrow {{z}^{2}}={{x}^{2}}+{{y}^{2}}$ --------- (4)
Now, we will solve equation (3), which is
$z=\sqrt{2-{{x}^{2}}-{{y}^{2}}}$
Now, we will take the square on both sides in the above equation, we get
$\Rightarrow {{z}^{2}}={{\left( \sqrt{2-{{x}^{2}}-{{y}^{2}}} \right)}^{2}}$
On further solving the above equation, we get
$\Rightarrow {{z}^{2}}=2-{{x}^{2}}-{{y}^{2}}$
Now, we will add ${{x}^{2}}+{{y}^{2}}$ in the above equation, we get
$\Rightarrow {{z}^{2}}+{{x}^{2}}+{{y}^{2}}=2-{{x}^{2}}-{{y}^{2}}+{{x}^{2}}+{{y}^{2}}$
As we know, the same terms with opposite signs cancel out each other, thus we get
$\Rightarrow {{z}^{2}}+{{x}^{2}}+{{y}^{2}}=2$
Therefore, we get
$\Rightarrow {{x}^{2}}+{{y}^{2}}+{{z}^{2}}=2$ ---------- (5)
Thus, we know that the above equation is an equation of a sphere, it implies the radius is equal to $\sqrt{2}$
Thus, the value of $\rho =\sqrt{2}$ --------- (6)
Therefore, the range of z is $\left[ 0,\sqrt{2} \right]$ -------- (7)
Now, we will solve the equation (4) and (5), to get the value of z, that is we will substitute the value of equation (4) in equation (5), we get
$\Rightarrow {{z}^{2}}+{{z}^{2}}=2$
$\Rightarrow 2{{z}^{2}}=2$
Now, we will divide 2 on both sides in the above equation, we get
$\Rightarrow \dfrac{2}{2}{{z}^{2}}=\dfrac{2}{2}$
On further solving, we get
$\Rightarrow {{z}^{2}}=1$
On taking the square root on both sides in the above equation, we get
$\Rightarrow \sqrt{{{z}^{2}}}=\sqrt{1}$
Therefore, we get
$\Rightarrow z=\pm 1$
Therefore, the value of z is equal to 1 -------- (8)
Also, we know the conversion of z is $\rho \cos \phi $ , therefore we get
$z=\rho \cos \phi $
Thus, we will substitute the value of equation (6) and (8) in the above equation, that is
$\Rightarrow 1=\sqrt{2}\cos \phi $
Now, we will divide $\sqrt{2}$ on both sides in the above equation, we get
$\Rightarrow \dfrac{1}{\sqrt{2}}=\dfrac{\sqrt{2}}{\sqrt{2}}\cos \phi $
Therefore, we get
$\Rightarrow \dfrac{1}{\sqrt{2}}=\cos \phi $
Also, we know that cos function is $\dfrac{1}{\sqrt{2}}$ when the angle is equal to $\dfrac{\pi }{4}$ .
Hence $\rho =\dfrac{\pi }{4}$
Thus, the range of $\rho $ is $\left[ 0,\dfrac{\pi }{4} \right]$ ------- (9)
Now, we will find the value of $\theta $ , that is we know that the unit circle is imposed on the xy-plane where the positive side of x-axis is equal to 0. Also, the complete circle has the range equal to $[0,2\pi ]$ . But in this case, the solid given to us is the one-fourth of the circle.
Therefore, the range of $\theta $ is equal to $\left[ 0,\dfrac{\pi }{2} \right]$ ------- (10)
Thus, from equation (7), (9), and (10), we get the new limits for our integration, that is
\[\Rightarrow \int_{0}^{\dfrac{\pi }{4}}{\int_{0}^{\dfrac{\pi }{2}}{\int_{0}^{\sqrt{2}}{{}}}}\] --------- (11)
Now we have to convert the integrand from rectangular to cylindrical coordinates, that is
$\begin{align}
& x=\rho \sin \phi \cos \theta \\
& y=\rho \sin \phi \sin \theta \\
& dzdydx={{\rho }^{2}}\sin \phi \left( d\rho \right)\left( d\theta \right)\left( d\phi \right) \\
\end{align}$ ----------- (12)
Thus, now we will combine the value of equation (11) and (12), to get the required value of the integral into the cylindrical and spherical coordinates, we get
\[\Rightarrow \int_{0}^{\dfrac{\pi }{4}}{\int_{0}^{\dfrac{\pi }{2}}{\int_{0}^{\sqrt{2}}{\left( \rho \sin \phi \cos \theta \right)\left( \rho \sin \phi \sin \theta \right){{\rho }^{2}}\sin \phi \left( d\rho \right)\left( d\theta \right)\left( d\phi \right)}}}\]
On further simplification, we get
\[\Rightarrow \int_{0}^{\dfrac{\pi }{4}}{\int_{0}^{\dfrac{\pi }{2}}{\int_{0}^{\sqrt{2}}{{{\rho }^{4}}{{\sin }^{3}}\phi \cos \theta \sin \theta \left( d\rho \right)\left( d\theta \right)\left( d\phi \right)}}}\]
Therefore, for the integral $\int_{0}^{1}{\int_{0}^{\sqrt{1-{{x}^{2}}}}{\int_{\sqrt{{{x}^{2}}+{{y}^{2}}}}^{\sqrt{2-{{x}^{2}}-{{y}^{2}}}}{xydzdydx}}}$ , its values in cylindrical or spherical coordinates is \[\int_{0}^{\dfrac{\pi }{4}}{\int_{0}^{\dfrac{\pi }{2}}{\int_{0}^{\sqrt{2}}{{{\rho }^{4}}{{\sin }^{3}}\phi \cos \theta \sin \theta \left( d\rho \right)\left( d\theta \right)\left( d\phi \right)}}}\] .
Note: While solving this problem, do mention all the steps properly to avoid calculations. Always remember that z changes to $\rho $ , y changes to $\theta $ and x changes to $\phi $ . Also, do not forget to mention changing the xy given in the integrand in the cylindrical coordinates.
Complete step-by-step solution:
According to the problem, we have to find the cylindrical or spherical coordinates from a definite integral.
Thus, we will apply the polar form to get the solution.
The integral given to us is $\int_{0}^{1}{\int_{0}^{\sqrt{1-{{x}^{2}}}}{\int_{\sqrt{{{x}^{2}}+{{y}^{2}}}}^{\sqrt{2-{{x}^{2}}-{{y}^{2}}}}{xydzdydx}}}$ --------- (1)
So, from equation (1), we get the value of the limit equals to
$\sqrt{{{x}^{2}}+{{y}^{2}}}\le z\le \sqrt{2-{{x}^{2}}-{{y}^{2}}}$
$0\le y\le \sqrt{1-{{x}^{2}}}$
$0\le x\le 1$
Now, we will first solve the z-domain, that is
$z=\sqrt{{{x}^{2}}+{{y}^{2}}}$ ------- (2) and
$z=\sqrt{2-{{x}^{2}}-{{y}^{2}}}$ ---------- (3)
Now, we will solve equation (2), which is
$z=\sqrt{{{x}^{2}}+{{y}^{2}}}$
So, we will square both sides in the above equation, we get
$\Rightarrow {{z}^{2}}={{\left( \sqrt{{{x}^{2}}+{{y}^{2}}} \right)}^{2}}$
On further solving the above problem, we get
$\Rightarrow {{z}^{2}}={{x}^{2}}+{{y}^{2}}$ --------- (4)
Now, we will solve equation (3), which is
$z=\sqrt{2-{{x}^{2}}-{{y}^{2}}}$
Now, we will take the square on both sides in the above equation, we get
$\Rightarrow {{z}^{2}}={{\left( \sqrt{2-{{x}^{2}}-{{y}^{2}}} \right)}^{2}}$
On further solving the above equation, we get
$\Rightarrow {{z}^{2}}=2-{{x}^{2}}-{{y}^{2}}$
Now, we will add ${{x}^{2}}+{{y}^{2}}$ in the above equation, we get
$\Rightarrow {{z}^{2}}+{{x}^{2}}+{{y}^{2}}=2-{{x}^{2}}-{{y}^{2}}+{{x}^{2}}+{{y}^{2}}$
As we know, the same terms with opposite signs cancel out each other, thus we get
$\Rightarrow {{z}^{2}}+{{x}^{2}}+{{y}^{2}}=2$
Therefore, we get
$\Rightarrow {{x}^{2}}+{{y}^{2}}+{{z}^{2}}=2$ ---------- (5)
Thus, we know that the above equation is an equation of a sphere, it implies the radius is equal to $\sqrt{2}$
Thus, the value of $\rho =\sqrt{2}$ --------- (6)
Therefore, the range of z is $\left[ 0,\sqrt{2} \right]$ -------- (7)
Now, we will solve the equation (4) and (5), to get the value of z, that is we will substitute the value of equation (4) in equation (5), we get
$\Rightarrow {{z}^{2}}+{{z}^{2}}=2$
$\Rightarrow 2{{z}^{2}}=2$
Now, we will divide 2 on both sides in the above equation, we get
$\Rightarrow \dfrac{2}{2}{{z}^{2}}=\dfrac{2}{2}$
On further solving, we get
$\Rightarrow {{z}^{2}}=1$
On taking the square root on both sides in the above equation, we get
$\Rightarrow \sqrt{{{z}^{2}}}=\sqrt{1}$
Therefore, we get
$\Rightarrow z=\pm 1$
Therefore, the value of z is equal to 1 -------- (8)
Also, we know the conversion of z is $\rho \cos \phi $ , therefore we get
$z=\rho \cos \phi $
Thus, we will substitute the value of equation (6) and (8) in the above equation, that is
$\Rightarrow 1=\sqrt{2}\cos \phi $
Now, we will divide $\sqrt{2}$ on both sides in the above equation, we get
$\Rightarrow \dfrac{1}{\sqrt{2}}=\dfrac{\sqrt{2}}{\sqrt{2}}\cos \phi $
Therefore, we get
$\Rightarrow \dfrac{1}{\sqrt{2}}=\cos \phi $
Also, we know that cos function is $\dfrac{1}{\sqrt{2}}$ when the angle is equal to $\dfrac{\pi }{4}$ .
Hence $\rho =\dfrac{\pi }{4}$
Thus, the range of $\rho $ is $\left[ 0,\dfrac{\pi }{4} \right]$ ------- (9)
Now, we will find the value of $\theta $ , that is we know that the unit circle is imposed on the xy-plane where the positive side of x-axis is equal to 0. Also, the complete circle has the range equal to $[0,2\pi ]$ . But in this case, the solid given to us is the one-fourth of the circle.
Therefore, the range of $\theta $ is equal to $\left[ 0,\dfrac{\pi }{2} \right]$ ------- (10)
Thus, from equation (7), (9), and (10), we get the new limits for our integration, that is
\[\Rightarrow \int_{0}^{\dfrac{\pi }{4}}{\int_{0}^{\dfrac{\pi }{2}}{\int_{0}^{\sqrt{2}}{{}}}}\] --------- (11)
Now we have to convert the integrand from rectangular to cylindrical coordinates, that is
$\begin{align}
& x=\rho \sin \phi \cos \theta \\
& y=\rho \sin \phi \sin \theta \\
& dzdydx={{\rho }^{2}}\sin \phi \left( d\rho \right)\left( d\theta \right)\left( d\phi \right) \\
\end{align}$ ----------- (12)
Thus, now we will combine the value of equation (11) and (12), to get the required value of the integral into the cylindrical and spherical coordinates, we get
\[\Rightarrow \int_{0}^{\dfrac{\pi }{4}}{\int_{0}^{\dfrac{\pi }{2}}{\int_{0}^{\sqrt{2}}{\left( \rho \sin \phi \cos \theta \right)\left( \rho \sin \phi \sin \theta \right){{\rho }^{2}}\sin \phi \left( d\rho \right)\left( d\theta \right)\left( d\phi \right)}}}\]
On further simplification, we get
\[\Rightarrow \int_{0}^{\dfrac{\pi }{4}}{\int_{0}^{\dfrac{\pi }{2}}{\int_{0}^{\sqrt{2}}{{{\rho }^{4}}{{\sin }^{3}}\phi \cos \theta \sin \theta \left( d\rho \right)\left( d\theta \right)\left( d\phi \right)}}}\]
Therefore, for the integral $\int_{0}^{1}{\int_{0}^{\sqrt{1-{{x}^{2}}}}{\int_{\sqrt{{{x}^{2}}+{{y}^{2}}}}^{\sqrt{2-{{x}^{2}}-{{y}^{2}}}}{xydzdydx}}}$ , its values in cylindrical or spherical coordinates is \[\int_{0}^{\dfrac{\pi }{4}}{\int_{0}^{\dfrac{\pi }{2}}{\int_{0}^{\sqrt{2}}{{{\rho }^{4}}{{\sin }^{3}}\phi \cos \theta \sin \theta \left( d\rho \right)\left( d\theta \right)\left( d\phi \right)}}}\] .
Note: While solving this problem, do mention all the steps properly to avoid calculations. Always remember that z changes to $\rho $ , y changes to $\theta $ and x changes to $\phi $ . Also, do not forget to mention changing the xy given in the integrand in the cylindrical coordinates.
Recently Updated Pages
Which of the following graphs shows the variation of class 12 physics CBSE

Draw a labelled diagram of the human male reproductive class 12 biology CBSE

Describe the experiment to compare the emf of two cells class 12 physics CBSE

What is standard hydrogen electrode

What is conventional current and electric current class 12 physics CBSE

2Bromopentane is treated with an alcoholic KOH solution class 12 chemistry CBSE

Trending doubts
Draw a labelled sketch of the human eye class 12 physics CBSE

Which are the Top 10 Largest Countries of the World?

Differentiate between homogeneous and heterogeneous class 12 chemistry CBSE

Draw ray diagrams each showing i myopic eye and ii class 12 physics CBSE

Which is the correct genotypic ratio of mendel dihybrid class 12 biology CBSE

What is the Full Form of PVC, PET, HDPE, LDPE, PP and PS ?

