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Math Help - need help please!!!

  1. #1
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    need help please!!!

    need help please!!!-assignment-8-q1.bmp
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    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by wik_chick88 View Post
    Click image for larger version. 

Name:	assignment 8 q1.bmp 
Views:	12 
Size:	406.8 KB 
ID:	7891
    I can't read it! Can you try to type out the question, using LaTeX?

    --Chris
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    Quote Originally Posted by Chris L T521 View Post
    I can't read it! Can you try to type out the question, using LaTeX?

    --Chris
    haha well i can almost type it out using latex BUT i cant do the double integral symbol with a circle attaching them. the symbol also has an S down the bottom...it sort of looks like \oint but with 2 integral signs...can you help??
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  4. #4
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    maybe... \int\int\limits_{S}
    ???? (dont know whether this will work or not...
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  5. #5
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by wik_chick88 View Post
    maybe... \int\int\limits_{S}
    ???? (dont know whether this will work or not...
    I'll keep in mind what you mean concerning the integral, but what is the question asking?

    --Chris
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    Quote Originally Posted by Chris L T521 View Post
    I'll keep in mind what you mean concerning the integral, but what is the question asking?

    --Chris
    the question is:

    evaluate
    need help please!!!-assignment-8-q1-3.bmp
    where F = 4xzi - y^2j + yzk and S is the surface of the cube bounded by the planes x = 0, x = 1, y = 0, y = 1, z = 0 and z = 1/
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  7. #7
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by wik_chick88 View Post
    the question is:

    evaluate
    Click image for larger version. 

Name:	assignment 8 q1 3.bmp 
Views:	7 
Size:	247.9 KB 
ID:	7892
    where F = 4xzi - y^2j + yzk and S is the surface of the cube bounded by the planes x = 0, x = 1, y = 0, y = 1, z = 0 and z = 1/
    If your integral means the same thing as \iint\limits_{\sigma}\bold F\cdot\bold n\,dS, then we can make life a ton easier and apply the divergence theorem which states:

    \iint\limits_{\sigma}\bold F\cdot\bold n\,dS=\iiint\limits_G \text{div}\,\bold F \,dV.

    So in our case, \iint\limits_{\sigma}\bold F\cdot\bold n\,dS=\iiint\limits_G \text{div}\,\bold F \,dV=\int_0^1\int_0^1\int_0^1\left(4z-y\right)\,dz\,dy\,dx

    --Chris
    Last edited by Chris L T521; September 24th 2008 at 11:04 PM.
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    Quote Originally Posted by Chris L T521 View Post
    If your integral means the same thing as \iint\limits_{\sigma}\bold F\cdot\bold n\,dS, then we can make life a ton easier and apply the divergence theorem which states:

    \iint\limits_{\sigma}\bold F\cdot\bold n\,dS=\iiint\limits_G \text{div}\,\bold F \,dV.

    So in our case, \iint\limits_{\sigma}\bold F\cdot\bold n\,dS=\iiint\limits_G \text{div}\,\bold F \,dV=\int_0^1\int_0^1\int_0^1\left(4z-y\right)\,dz\,dy\,dx

    --Chris
    thanks so much Chris!! i got

    =\int_0^1\int_0^1\int_0^1\left(4z-y\right)\,dz\,dy\,dx

    = 1.5

    is that right??
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  9. #9
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by wik_chick88 View Post
    thanks so much Chris!! i got

    =\int_0^1\int_0^1\int_0^1\left(4z-y\right)\,dz\,dy\,dx

    = 1.5

    is that right??
    Yes!

    --Chris
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