# Double or Triple integration (Find the area ) Uncommon question

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• Mar 5th 2013, 09:15 PM
happymatthematics
Double or Triple integration (Find the area ) Uncommon question
The question is:
Attachment 27369
Please click the picture above.
I let x^2+y^2=a^2 be the vertical cylinder, and I tried to find
1)the intersections between x^2+y^2=a^2 and z=2xy
2)the intersections between x^2+y^2=a^2 and z=x^2+y^2
and then don't know how to do.
I need to show the two area is the same, but i don't know how to show.
• Mar 6th 2013, 12:10 AM
chiro
Re: Double or Triple integration (Find the area ) Uncommon question
Hey happymatthematics.

What did you get for the intersections? (Once you have these then they become the limits for your area integral).
• Mar 6th 2013, 03:43 AM
happymatthematics
Re: Double or Triple integration (Find the area ) Uncommon question
hello chiro,
the following is my attempt.
Attachment 27378

I found them in parametric form.
I now have three variables, including x, y, z, but I learnt to find area by double integration. so how to find area of three variables?
• Mar 6th 2013, 05:19 PM
chiro
Re: Double or Triple integration (Find the area ) Uncommon question
What are your limits of integration? You will be integrating over a region with specific limits.

Once you show the limits (and how you derived them), then we can take it from there.