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ABCD is a regular tetrahedron. AB=BC=CA=AD=BD=CD= 8cm.

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ABCD is a regular tetrahedron. AB=BC=CA=AD=BD=CD= 8cm.

  1. Calculate the angle between line AD and plane ABC. 
  2. Calculate the angle between planes ABD and ABC 

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  1. Sin 60º = 4/AO 
    AO = 4/Sin60º   =4.619cm
    sukmathsp2ans14a   
    Cosθ = 4.619/8   
    θ = 54.73º
  2.   
    sukmathsp2ans14bi 
    h = √(82 - 42)
    = 6.928cm
    sukmathsp2ans14bii
    Cos θ = 2.309/6.928
    θ = 70.53º
     

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