I need to setup the triple integral in cartesian coordinates to solve the volume of f(x, y, z)=z inside the cylinder x^2+y^2=10 and outside the hyperboloid x^2+y^2-z^2=1 in the first octant.

Intomathymnma

Intomathymnma

Answered question

2022-07-21

Finding the volume of f ( x , y , z ) = z inside the cylinder and outside the hyperboloid
I need to setup the triple integral in cartesian coordinates to solve the volume of f ( x , y , z ) = z inside the cylinder x 2 + y 2 = 10 and outside the hyperboloid x 2 + y 2 z 2 = 1 in the first octant.
What I did so far is to find the intersection between the cylinder and hyperboloid so that I can find the bounds for z. Actually, I am uncertain if finding this intersection is a right procedure.
10 z 2 = 1 z = 3
My bounds for z is 0 z 3 since the volume is also bounded by the first octant. My bounds for y is 1 x 2 y 10 x 2 . Lastly, my bounds for x is 1 x 10 . My iterated integral for this one will be like this 1 10 1 x 2 10 x 2 0 3 z d z d y d x
Do I miss something here?

Answer & Explanation

jbacapzh

jbacapzh

Beginner2022-07-22Added 18 answers

Step 1
No that is not correct. Both z bounds cannot be constant.
It is much easier in cylindrical coordinates but if you have to set it up in cartesian coordinates,
Integrating wrt z first, 0 z x 2 + y 2 1 .
1) For 0 x 1, y is bound between two circles in XY-plane ( x 2 + y 2 = 1 and x 2 + y 2 = 10).
1 x 2 y 10 x 2
Step 2
2) For 1 x 10 , y is bound between x-axis and circle x 2 + y 2 = 10.
So the integral would be, 0 1 1 x 2 10 x 2 0 x 2 + y 2 1 z   d z   d y   d x     +
1 10 0 10 x 2 0 x 2 + y 2 1 z   d z   d y   d x

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