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Question about a notation.

  1. Apr 21, 2010 #1
    Hey Everyone,

    This may be a silly question and I am able to interpret the intention of the notation but I am just curious exactly what it is.

    I am attaching an image of the page out of my text book and it is near the bottom. C = C1 U C2.

    Sorry again if this is a silly question, I just wanted to make sure I understand this notation outside the context of this problem. I am sure I have seen it before but I am still not sure.


    Attached Files:

  2. jcsd
  3. Apr 21, 2010 #2


    Staff: Mentor

    Your attachment hasn't been approved yet.

    Are you asking about C1 U C2? The U symbol is "union".

    x is an element of A U B if x is an element of A or x is an element of B. The "or" really means "and/or" to include elements that might be in both sets.

    For example, if A = {1, 2, 3, 5, 8} and B = {3, 6, 9, 12}, then A U B = {1, 2, 3, 5, 6, 8, 9, 12}.

    Another set operation is "intersection" [itex]\bigcap[/itex]. x is an element of A [itex]\bigcap[/itex] B if x is an element of A and x is an element of B. Using the same example, A [itex]\bigcap[/itex] B = {3}.
  4. Apr 22, 2010 #3


    User Avatar
    Science Advisor

    In this case [itex]C_1[/itex] is the straight line from (0, 2) to (3, 2) and [itex]C_2[/itex] is the straight line from (3,2) to (3,5). "[itex]C= C_1\cup C_2[/itex]" is the two paths put together: to integrate along C, integrate along [itex]C_1[/itex] and [itex]C_2[/itex] and add the two integrals.
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