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Homework Help: 3 Dimensional problem

  1. Aug 30, 2011 #1
    1. The problem statement, all variables and given/known data

    ABCD is a regular tetrahedron, i.e. its sides are of equal length. E and F are the mid-points of AB and CD respectively. Find the angle between

    a) the plane ABEF and the plane CDEF
    b) the plane ABEF and the line AC
    c)the line AC and the line EF

    2. Relevant equations

    3. The attempt at a solution

    For (a), does plane ABEF same as plane ABF while plane CDEF same as CDE?

    Can anyone give me some hints? Thank you.
  2. jcsd
  3. Aug 30, 2011 #2


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    Science Advisor
    Homework Helper
    Gold Member

    Yes to both of those questions. I would work this problem by finding the coordinates of the three points you have used for each plane, calculating the normals to the planes and finding the angle between the normals.
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