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Planes in R3 Properties

  1. Aug 28, 2011 #1
    Hello I am having a problem with the following question.

    1. The problem statement, all variables and given/known data
    Determine which statements are true in 3. (Select all that apply.)

    (a) Two lines parallel to a third line are parallel.
    (b) Two lines perpendicular to a third line are parallel.
    (c) Two planes parallel to a third plane are parallel.
    (d) Two planes perpendicular to a third plane are parallel.
    (e) Two lines parallel to a plane are parallel.
    (f) Two lines perpendicular to a plane are parallel.
    (g) Two planes parallel to a line are parallel.
    (h) Two planes perpendicular to a line are parallel.
    (i) Two planes either intersect or are parallel.
    (j) Two lines either intersect or are parallel.
    (k) A plane and a line either intersect or are parallel.

    2. Relevant equations
    None.

    3. The attempt at a solution
    This is what I did (i am going to write it with T/F)
    a) F - they maybe skew
    b) T
    c) T
    d) T
    e) F - they maybe skew
    f) T
    g) F - they may intersect
    h) T
    i) T
    j) F - Skew
    k) T? - I choose true but a line can be contained in a plane. Are they different things? Or I have a problem in other answers.

    Thanks in advance,
    Gasim
     
  2. jcsd
  3. Aug 28, 2011 #2

    Dick

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    If by '3' you mean three dimensional euclidean space, then a) is already wrong. What's your definition of parallel? Can you give an example where the two lines are skew?
     
    Last edited: Aug 28, 2011
  4. Aug 28, 2011 #3
    if two lines are skew they are neither intersecting nor are parallel
     
  5. Aug 28, 2011 #4

    Dick

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    I asked, what's your DEFINITION of parallel?
     
  6. Aug 28, 2011 #5
    Oh. Sorry. I'll draw it tonight. I just have to rush to a store right. Sorry about that. Thanks.
     
  7. Aug 28, 2011 #6

    Dick

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    S'ok, but you'll probably have to do more than draw it. That wouldn't likely be useful. State the definition in words.
     
  8. Aug 28, 2011 #7
    Actually, I get it. A is true but B is false. Am I right on this?

    Skew is like one of them for example is a straight line to the right and the other one in the bottom of it towards me. Its not a good example but I hope its right.
     
  9. Aug 28, 2011 #8

    Dick

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    Correct so far.
     
  10. Aug 28, 2011 #9
    Alright, I am going to be working on this tonight. Thank you for pointing that out!
     
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