Results 1 to 6 of 6

Math Help - Hey guys! What operation is this symbol?

  1. #1
    Newbie
    Joined
    Jun 2012
    From
    Liverpool
    Posts
    3

    Hey guys! What operation is this symbol?

    Hey guys. To introduce myself to the forum, I'm a first (going on second) year Computer Science student from Liverpool UK. Just a quick question on a symbol I have come across;
    Hey guys! What operation is this symbol?-2012-06-27-16.38.21.jpg
    I know the union of sets, A \cup B joins all elements in A and B. As far as I can tell from the description it is the union of all the sets $A_{x}$ where x is an element of X. The lines being the cardinality of this set which has been joined (union).
    Am I close at all to it's meaning? If so, could you then have a big intersect symbol to intersect the sets produced. There is also an example later with b \in C under the big union symbol, is this just a condition for the union operation?

    Thanks guys

    Phil
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,646
    Thanks
    1596
    Awards
    1

    Re: Hey guys! What operation is this symbol?

    Quote Originally Posted by philleonard View Post
    Hey guys. To introduce myself to the forum, I'm a first (going on second) year Computer Science student from Liverpool UK. Just a quick question on a symbol I have come across;
    Click image for larger version. 

Name:	2012-06-27 16.38.21.jpg 
Views:	8 
Size:	1.04 MB 
ID:	24174
    I know the union of sets, A \cup B joins all elements in A and B. As far as I can tell from the description it is the union of all the sets $A_{x}$ where x is an element of X. The lines being the cardinality of this set which has been joined (union).
    Am I close at all to it's meaning? If so, could you then have a big intersect symbol to intersect the sets produced. There is also an example later with b \in C under the big union symbol, is this just a condition for the union operation?
    You realize that it is very hard to read the image.

    The notation |A\cup B\cup C| stands for the number of elements in at least one of A,~B,\text{ or }C.

    It equal to |A|+|B|+| C|-|A\cap B|-|A\cap C|-| B\cap C|+|A\cap B\cap C|.

    Now please tell us what you need explaining.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,535
    Thanks
    778

    Re: Hey guys! What operation is this symbol?

    Quote Originally Posted by philleonard View Post
    As far as I can tell from the description it is the union of all the sets $A_{x}$ where x is an element of X.
    Yes, \bigcup\{A_x:x\in X\} is the union of A_x for all x\in X.

    Quote Originally Posted by philleonard View Post
    could you then have a big intersect symbol to intersect the sets produced.
    Yes, \bigcup can be replaced by \bigcap to mean the intersection of all A_x.

    Quote Originally Posted by philleonard View Post
    There is also an example later with b \in C under the big union symbol, is this just a condition for the union operation?
    The big union symbol \bigcup is used in two ways. One can write \bigcup A if A is a family of sets: A=\{A_1,\dots,A_n\}. In this case, \bigcup A means A_1\cup\dots\cup A_n. Alternatively, by analogy with the summation symbol \sum, one can write \bigcup_{i\in I}A_i to mean the union of A_i for all i\in I. Thus, \bigcup\{A_x: x\in X\}=\bigcup_{x\in X}A_x.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member
    Joined
    Jun 2012
    From
    AZ
    Posts
    616
    Thanks
    97

    Re: Hey guys! What operation is this symbol?

    Quote Originally Posted by philleonard View Post
    As far as I can tell from the description it is the union of all the sets $A_{x}$ where x is an element of X. The lines being the cardinality of this set which has been joined (union).
    That is correct. The |...| represent the magnitude of that set.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Jun 2012
    From
    Liverpool
    Posts
    3

    Re: Hey guys! What operation is this symbol?

    Click on the image for a larger view please. Thanks for taking time to explain that though.
    Edit: Sorry just seen all the new posts too, will read now. Thanks
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Newbie
    Joined
    Jun 2012
    From
    Liverpool
    Posts
    3

    Re: Hey guys! What operation is this symbol?

    Thank you so much @emakarov Fantastic explanation!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Hello guys I need some help! :(
    Posted in the Algebra Forum
    Replies: 3
    Last Post: June 4th 2012, 04:47 AM
  2. Hi Guys!
    Posted in the New Users Forum
    Replies: 0
    Last Post: May 27th 2012, 11:00 PM
  3. Hey Guys
    Posted in the New Users Forum
    Replies: 0
    Last Post: May 26th 2012, 09:19 PM
  4. Please what is this operation symbol?
    Posted in the Advanced Algebra Forum
    Replies: 7
    Last Post: April 17th 2011, 09:17 AM

Search Tags


/mathhelpforum @mathhelpforum