Need help in finding Limits of Integration (Calc 3)

In summary, to find the limits of integration for the given integral, you need to express the normal vector and the element of surface as functions of x and y. Then, the limits for x and y will be from 0 to infinity, while the limit for z will be 1-x-y. The normal vector will have components (a,b,c) and the element of surface will be dS = c*dx*dy.
  • #1
Arshad_Physic
51
1
Need help in finding Limits of Integration! :) (Calc 3)

Homework Statement



Evaluate


Integral: f * n dS, where "f" and "n" are vectors and "*" is DOT PRODUCT.

Where,

where
(a) f = (x2, ey, 1),

S: x + y + z = 1, x ≥ 0, y ≥ 0, z ≥

Homework Equations



ummm none

The Attempt at a Solution



So, I figured that:
r(u,v) = (u,v,1-u-v)
f (x(u),y(v)) = u2, ev, 1)

I also got N vector, which is 1.

BUT HOW DO I FIND THE INTEGRATION LIMITS?!

I know that "x ≥ 0, y ≥ 0, z ≥ ", but how does this help me? Are the integration limits from
0 to INFINITY?

PLease Help! I have been trying to think for 48 hours on this!

THanks!
 
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  • #2


The normal isn't 1, it's a vector, so it'll have compenents, what is the vector. You're integrating over a surface S, what is this surface?
 
  • #3


The integration limits are for x and y from 0 to infinite and for z equal to 1-x-y. Since f doesn't depend on z this doesn't matter.

n is the vector with magnitude 1 and direction normal to the surface x+y+z=1.

Find a way to express n in (a,b,c) notation and the element of surface dS as a function of dx and dy. Then [tex]f*n=ax^2+be^y+c[/tex].

dS will be dS=cdxdy.
 
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FAQ: Need help in finding Limits of Integration (Calc 3)

1. What is the purpose of finding limits of integration in Calc 3?

Finding limits of integration in Calc 3 is important because it helps us determine the bounds of a given region or volume. This is crucial in solving many real-world problems in fields such as physics, engineering, and economics.

2. How do I know which variable to integrate with respect to?

In most cases, the variable to integrate with respect to will be specified in the problem or given context. However, if it is not specified, you can choose either variable as long as the limits of integration are in terms of that variable. It is also important to consider which variable would result in a simpler integration process.

3. What are the common methods for finding limits of integration?

The most common methods for finding limits of integration in Calc 3 are using geometry, setting up and solving equations, and using symmetry. Geometry involves visualizing the region or volume and determining the boundaries. Setting up and solving equations involves using given equations or conditions to find the limits. Symmetry can also be used to simplify the process by taking advantage of symmetrical shapes or functions.

4. Are there any special cases in finding limits of integration?

Yes, there are a few special cases to consider when finding limits of integration. These include regions or volumes with curved boundaries, overlapping regions, and regions with holes. In these cases, it may be necessary to break up the region into smaller parts and find the limits of integration for each part separately.

5. How can I check if my limits of integration are correct?

One way to check if your limits of integration are correct is to graph the region or volume and see if the boundaries align with the limits you have found. Another method is to evaluate the integral using the found limits and see if the result matches the given conditions or expected outcome of the problem.

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