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    (Original post by james22)
    I have a suface in R^3 defined by F(x,y,z)=0 where

    F(x,y,z)=(z^2-x^4-a^2)(Y62-x^4-a^2+z^2)

    I need to find the unit normal at (0,0,a)

    I found the normal at this point and got (0,0,0) which isn't helpful. Is this right? If so what does it mean?
    Post your working. I'm not sure what Y62 means btw.
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    (Original post by Indeterminate)
    Post your working. I'm not sure what Y62 means btw.
    Typo

    I've just put it into wolfram alpha

    http://www.wolframalpha.com/input/?i=gradient+%28z^2-x^4-a^2%29%28y^2-x^4-a^2%2Bz^2%29

    and when I put (0,0,a) into the gradient I get (0,0,0).
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    Ignore this now, I made a huge mistake earlier in the question which makes this question obsolete. Sorry
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    (Original post by james22)
    Typo

    I've just put it into wolfram alpha

    http://www.wolframalpha.com/input/?i=gradient+%28z^2-x^4-a^2%29%28y^2-x^4-a^2%2Bz^2%29

    and when I put (0,0,a) into the gradient I get (0,0,0).
    Are you sure you've copied out the Q correctly, because the modulus of a unit vector must be 1, and

    |(0,0,0)| \neq 1
 
 
 
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