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Homework Help: Probability formula Question

  1. Jan 26, 2013 #1
    1. The problem statement, all variables and given/known data

    Show that the formula: P(AΔB) = P(A) + P(B) - 2P(A[itex]\bigcap[/itex]B)

    2. Relevant equations

    3. The attempt at a solution

    P(AΔB) = P(A) + P(B) - 2P(A[itex]\bigcap[/itex]B)

    P(AΔB) = P(A[itex]\bigcap B^{c}[/itex])[itex]\bigcup (A^{c}\bigcap B)[/itex]

    I don't know where to go from here. Thanks for any help.
  2. jcsd
  3. Jan 26, 2013 #2


    Staff: Mentor

    Show that the formula does what?
    Definition of P(AΔB), perhaps?
  4. Jan 26, 2013 #3


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    Science Advisor
    Homework Helper

    Hi GreenPrint! :smile:

    Hint: how would you prove area(AΔB) = area(A) + area(B) - 2area(A[itex]\bigcap[/itex]B) ? :wink:
  5. Jan 26, 2013 #4

    Ray Vickson

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    Use Venn diagrams; that's their purpose.
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