Hi, could someone explain step by step how to answer these questions please:

Calculate the volume:

1) z^2 + x^2 =1 and x+y+z=3, y=0

2) (x^2)/9 +(y^2)/4 =1, z=xy in the 1st quadrant

Thanks

- June 1st 2008, 05:09 PMSummitCould someone explain how to answer these 2 multiple integration questions please
Hi, could someone explain step by step how to answer these questions please:

Calculate the volume:

1) z^2 + x^2 =1 and x+y+z=3, y=0

2) (x^2)/9 +(y^2)/4 =1, z=xy in the 1st quadrant

Thanks - June 1st 2008, 06:11 PMTheEmptySet
Always draw a graph it helps you see the volume that you are trying to find.

The equation is a circluar cylindar of radius 1 centered on the y axis. It's bottom is the xz plane(y=0) and it is cut by the plane .

To find the volume I want to use cylindrical coordinates, but since the cylindar is tipped over lets use this change of coordinates.

Now we get the integral

You could have also set up a double integral using the same idea where y is your height function.

I hope this helps.

Good luck. - June 1st 2008, 06:26 PMTheEmptySet
Once again draw a graph.

The equation

Is an equation of an elliptic cylindar centered on the z axis. We are trying to find the volume under the surface z=xy inside the cylindar and in quadrant one.

the projection of the cylindar into the xy plane is the ellipse

We can islolate y in this expression to get

In the first quadrant

Now the inegral is

Good luck.