Triple Integral: Having trouble finding my y bounds

Saladsamurai
Messages
3,009
Reaction score
7

Homework Statement



I=\int\int\int_E x^2e^ydV where E is bounded by the parabolic cylinder

z=1-y^2 and the planes z=0 x=1 and x=-1

I know that the graph is a parabola that opens downwards and that has symmetry wrt the x-axis. It also stretches along the x-axis toward + and - infinity.

Can I get a hint here? :)
 
Physics news on Phys.org
Did you mean
I=\int\int\int_E x^2e^y\,dV ?
 
It's pretty close to being trivial. The parabola z= 1- y2 has z= 0 at y= -1 and y= 1 so projecting down on to xy=plane, we get the square -1< x< 1, -1< y< 1. The z- integral is taken from 0 to 1- y2, the y integral from -1 to 1, and the x integral from -1 to 1.
 
Avodyne said:
Did you mean
I=\int\int\int_E x^2e^y\,dV ?

I don't see any difference. So yes. :smile:
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top