multiple integrals: cylinder

Could you please help me with this problems??? 1)Find the volume of solid bounded by** planes** x+y+z=6, z=0 and the **cylinder**= x^2+y^2=4

2)Find the volume of solid bounded by** planes **z=3x,z=0and the **cylinder**= x^2+y^2=1

I can't find the results when I put the polar coordinates (Crying)

Re: multiple integrals: cylinder

Hint: In your triple integral in polar coordinates the limits on the z integral are 0 and 6-y-x, put the limits in polar form.

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Re: multiple integrals: cylinder

i posted an image to show you how i started..i used double integrals alike this problem Multiple Integrals 9: Finding Volume Problems (Cylinder) - YouTube ..but probably this way is wrong..it would help me if you could tell me you opinion!!!

Re: multiple integrals: cylinder

Your question is exactly like the 1 in the video. But I think he goes about it in a more complicated way. Put the whole problem into polar coordinates and integrate with respect to z first.