Math wizards please let yourselves be known!!

[Lady Freedom]

I have a math test tomorrow morning at 9am and I am still in a fog about all of it! HELP!!!

[Bill McBlueState]

1. Well, what's it about?

"Math" is a pretty big topic, as I'm sure you know. :)

[Lady Freedom]

2. This round is...

Sets and Notation
Subsets
Set Operations
Venn Diagrams
and Surveys

[YouthInAsia]

8. oh god....STOP!!!!!! I got nauseaus just READING those words.

math is terrifying. Sorry!

[Rabrrrrrr]

11. Math is not terrifying, though its REVELATIONS are terrifying,

because coming face to face with God is a terrifying encounter. And math is the language of God, and the path TO God.

[YouthInAsia]

16. well its terrifying to those of us who SUCK at it and have developed

a math PHOBIA. my mother says her luck will be, in order to get into heaven she'll have to answer a word problem. HAHAHAHA

[ForrestGump]

3. Here I come to save the day...

Good luck!

[Lady Freedom]

5. Thank Forrest! That was a big help!

:banghead: I an having trouble enough with REAL math as it is! Please don't bring fuzzy math into it to!!

[Lady Freedom]

4. Sets and Notation

If you use "C" as the set for the United States flag and list it like this: C={X/x is a color of the US flag}

Then how does x not represent the set?

[Lady Freedom]

6. kick

[mainegreen]

7. I think most of us forget that stuff the day after the test.

I know I've forgotten most of everything I learned after calc.

[aePrime]

9. Hmm

If you have C = {x : x is a color of the US flag}, you don't get a set of the flag (which would be a set of one element), you get a set of the colors: {red, white, blue}. The notation {x : x ...} or {x | x ...} is a way of defining a set. It basically says that we have a rule on the left hand side of the ":" and a list of elements to which to apply that rule on the right hand side. After we apply the rule to each element on the right hand side, that element is a part of our set. In this case, our rule is only "x", so we take the elements on the right hand side as they are.

In your example, you've defined your set twice, but using nonequivalent definitions. You first said, C is the set for the US flag (unless you meant to say colors). That would mean that C is the set of one element, {US flag}. As already stated, your set notation, however, lists {red, white, blue}.

So, if we have
F = {n : n is an integer and 1 < n < 5}

read, "The set of integers, n, such that n is greater than one and less than five."

F would be {2, 3, 4}

G = {x * 2 : x is an integers 0 < x < 6}
G would be {2, 4, 6, 8, 10}

[Rabrrrrrr]

12. aePrime already chimed in, but let me add my support to the idea

that you have given us the problem wrong. I, too, wonder if you meant that C is the set of COLORS of the United States Flag.

If you gave us the question EXACTLY as your teacher gave it, then you need to speak with your teacher about asking questions that are real.

[Lady Freedom]

19. Sure here

1. Explain what sort of elements are in the set
Example: C is the set of colors of the United States flag

2. List the elements in the set
C={red,white,blue}

3. Use set builder notation
C={x:x is a color of the Unite States flag}


my ?. what does "X" represent.

[Rabrrrrrr]

22. Okay, here's the first math lesson to offer you: be accurate.

Math doesn't deal with "feelings" or "close enough" or "well, that's what I meant".

You have copied the question wrong again.

You ask, "What does "X" represent", but you have no "X" in your question. You have, however, two "x"es.

Sure, this might seem anal and offensive, but math is a very anal practice.

The VERY FIRST step in being able to do math is to read literally, talk literally, and be accurate - exactly, spot on, accurate.

[Lady Freedom]

23. That is just it!

She is trying to use this to show use about sets and notation and I can't make head or tails of this because I have no idea where this "X" business comes in! No matter how much I read her on-line lechers!

And I can't get a strait answer from her!

[Rabrrrrrr]

25. Read and look at the problem EXACTLY AS WRITTEN

If there is an X that is different than an x. And an x is different than an x.

I'm being very serious here - in mathematics, NOTHING is wasted, everything is written and given for a precise and essential reason. If one spot has X and another has x, then you can know, by God, that they are talking about two entirely different things.

mathematics is absolutely THE MOST EFFICIENT language every invented; no redundancies, no room for "interpretation", no wasted characters.

Take a look at your problem again, and type it in EXACLTY as written.

[Lady Freedom]

28. that is how it is written. that is what is throwing me!

[Lady Freedom]

26. This is the whole section!

Sets are collection of objects, called elements or members. Sets can be decribed in diffrent ways.

1. Explain what sort of elements are in the set
Example: C is the set of colors of the United States flag

2. List the elements in the set
C={red,white,blue}

3. Use set builder notation
C={x:x is a color of the Unite States flag}


The last version is read "C is the set of all x such that x is a color of the United States Flag". It does notmean that x is in the set, but that x is a variable name representing the elelments in the set.


My ?= is x represents the colors somehow?

[aePrime]

24. He's right

I was really tempted to point out your 'x' and 'X' in the post to which I replied. In a problem, they can very well mean very different things.

In fact, they have a habit of doing that in probability and statistics with random variable names.

[aePrime]

27. 'x' is a dummy variable

'x', not 'X', as Rabrrrrrrrrrrrrrrrrrrrrrrrr (speaking of precise definitions) already pointed out.

When I look at set notation, I always consider the variable in the set builder notation to be a variable over which I iterate. That's probably just the computer scientist in me though.

x is simply a placeholder. On the right hand side of ":" you assign x every value that's listed there -- in this case, the three colors of the flag. For each value on the right hand side, you add it to the set using the rule on the left hand side. In this case, the rule on the left hand side doesn't modify it, and so it just adds the element to the set.

[aePrime]

29. Methinks I must be on ignore!

Alas, I'll spend my time drawing pictures of the FSM.

[Lady Freedom]

30. Sort of like ellipses?

[aePrime]

32. They're both used to specify sets

So in that way, they're similar.

But the ellipses are used to fill in when it's obvious what should go there.

F = {1, 2, 3, ..., 20}

Is the set including the integers from 1 to 20. The ellipses are used because the pattern's obvious.

If it's not obvious, ellipses shouldn't be used. For example,

G = {books, speakers, cans, CDs, ...}

That doesn't really tell you what's in the set. It would be more obvious in this form:

G = {x : x is an item on my desk}

So here we're adding all elements that are on my desk to a set. Here, x only has value within the set builder notation. We're saying "We're adding x to the set, where x is an item on my desk." We're not saying "x is a book", or "x is a CD", we're letting x represent all of the things on my desk, one at a time.

[Lady Freedom]

33. Thank You!

That makes more sence!

[Rabrrrrrr]

10. Sure - chiming in!

What you need to know? Gotta solve a three-variable differential equation?

[Crazy Guggenheim]

13. Anything on Minkowski Spaces?

[Rabrrrrrr]

14. Feynman diagrams? Fractional dimensions? Non-Euclidean geometry?

Come on - give us the fun stuff!

[Crazy Guggenheim]

15. Yeah now you got it!

[Rabrrrrrr]

17. Karpinsky Sieves? Appolonian Gaskets? Peano Curves? Cauchy Sequence?

[Lady Freedom]

20. that is after the midterms.

[HEyHEY]

18. And step forward to receive your wedgie!

[Lady Freedom]

21. There will be no wedgis on those...

that can save my GPA!

[entanglement]

31. I, for one, refuse to answer simple math questions

Now of you were to ask me about Mock-theta functions, or Lie algebras, I might be inclined to answer

:P

[aePrime]

34. Does P = NP?

[entanglement]

35. I actually have a wonderful proof for that

but it is too large to fit in a single DU post

:evilgrin:

[aePrime]

36. Ahh, 'tis a shame

It's been nagging at me lately, and nobody will give me a straight answer!