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Math Help - set algebra

  1. #1
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    set algebra

    Questions are following:

    Are the following statements true or false? If true, use two methods: element argument method and the laws of set theory to prove it; if false, give a counter exmple to disprove it.

    Thank you!
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  2. #2
    Super Member angel.white's Avatar
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    Quote Originally Posted by The_Hater View Post
    Questions are following:

    Are the following statements true or false? If true, use two methods: element argument method and the laws of set theory to prove it; if false, give a counter exmple to disprove it.

    Thank you!
    The second one is true, think of 3 circles intersecting, B unioned with C will be two of the circles acting as a single entity, and that entity will remove part of A. So A will be a circle with what looks like two "bites" out of it.

    Then the right half says A-B so B takes a "bite" out of A. and A-C so C takes a "bite" out of A, and the leftovers from each of these are intersected together. Since the bite that B took will not be there, it has nothing to intersect, and since the bite that C took will not be there, it has nothing to intersect, so all that will remain from A-B intersecting A-C is A that was not removed in either operation. So A will have two "bites" out of it.

    So I guess think of A as a cookie ^_^ and BUC as a person with two mouths taking a single bite, and (A-B) U (A-C) as two people who each take a bite out of the same cookie.

    ...Or you could probably search and find some mathematical equation to apply to this, or write a big long proof, or convert to set builder notation where you can manipulate easier.

    As for the first one, I'm not familiar with the triangle in your notation, so I won't comment on it.
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  3. #3
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    thats the symmetric difference defined by  A \triangle B = (A-B) \cup (B-A) .
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