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Math Help - angle between plane and plane

  1. #1
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    angle between plane and plane

    can someone explain why when z=0 , n =k https://www.flickr.com/photos/123101...3/14096908607/
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  2. #2
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    Re: angle between plane and plane

    Quote Originally Posted by delso View Post
    can someone explain why when z=0 , n =k https://www.flickr.com/photos/123101...3/14096908607/
    The plane $z=0$ is the $xy-$plane, $\{(x,y,0)\}$.
    The vector $\vec{k}=<0,0,1>$ is normal to each of those $<x,y,0>$.
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    Re: angle between plane and plane

    do u mean in order to get the scalar product =0, you equate (x, y, 0 ) dot (0, 0 , 1) to 0 ? but in order to get 0 , why must the value be 1 ? the unknown value cant be other than 1?
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    Re: angle between plane and plane

    Quote Originally Posted by delso View Post
    do u mean in order to get the scalar product =0, you equate (x, y, 0 ) dot (0, 0 , 1) to 0 ? but in order to get 0 , why must the value be 1 ? the unknown value cant be other than 1?
    How much do you know about vector geometry?
    Do you know that $\vec{i}=<1,0,0>,~\vec{j}=<0,1,0>,~\&~\vec{k}=<0,0 ,1>,$ is the basics for vector spaces.

    $\vec{i}$ is the normal for the $yz$-plane; $\vec{j}$ is the normal for the $xz$-plane; $\vec{k}$ is the normal for the $xy$-plane.

    It seems to me that you are very confused about all of this material.
    Is this an online course?
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  5. #5
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    Re: angle between plane and plane

    If you are still confused, perhaps this will help. The coefficients for x and y are both zero. So, the plane z=0 is the same as

    0\cdot x + 0\cdot y + 1\cdot z = 0

    So, the normal is:

    \vec{n} = 0\cdot \vec{i} + 0\cdot \vec{j} + 1 \cdot \vec{k}

    You find the normal for that plane just as you would find the normal for any other plane.
    Thanks from delso
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  6. #6
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    Re: angle between plane and plane

    sorry my basic of vector is too weak. i cant really undersatnd while i 'm studying this chapter .
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