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Calculate some things about a tetrahedron

  1. Mar 22, 2007 #1
    Question Statement:
    Each surface of a tetrahedron ABCD is an equilateral triangle with each side 2 units long. The midpoint of AB and CD are L and M respectively. Calculate, by giving your answers correct to 3 s.f. or to the nearest 0.1 degree,

    a) The length of the perpendicular from A to the plane BCD
    b) The angle between the surface ACD and BCD
    c) Angle between AB and the plane BCD

    My Attempt So Far :
    I have solved part A and B. The only part that confuse me is part C.
    My calculation :
    let the angle between AB and the plane BCD be x.
    The perpendicular distance from A to the plane BCD be p.
    So sin x = p/AB = 1.63/2

    But the answer given is x = 53.1 degree, which is slightly smaller than the answer I found.

    Is the method I used wrong?
  2. jcsd
  3. Mar 22, 2007 #2
    Just looking quickly the answer you have may be less due to rounding error. How much less is your answer than the answer given in the book?
  4. Mar 23, 2007 #3
    1 degree. The answer given is 53.1 degree, wheres mine is about 54 degrees.
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