Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

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**JaneFairfax****Member**- Registered: 2007-02-23
- Posts: 6,868

On Only Connect last evening, the Mathematicians were playing agains the Wordsmiths. The Mathematicians won!

Only Connect is a series of word-quiz game shows currently being shown on Mondays 20:3021:00 on BBC Four. I was surprised the Mathematicians took ages to work out the value of . And there was a slight mistake on the show. is not but where is any integer.

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**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

The mathematicians were surprised at themselves too. Presumably the pressure was getting to them a bit.

The mistake that I was more annoyed at was when the show said that ≡ meant "equal by definition".

Why did the vector cross the road?

It wanted to be normal.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,771

Hi mathsyperson;

I have seen ≡ as meaning an identity or exactly equal.

*Last edited by bobbym (2009-07-21 07:49:14)*

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

Yes, that's how I know it as well. "Equal by definition" is different though.

≡ is used for statements like (x+1)² ≡ x² + 2x + 1.

They're identical as opposed to equal, because the value of x doesn't change the validity.

Equal by definition , :=, is used to 'shorthandedly' define a new variable.

Let's say I want to use a function given by that expression.

I could say "Now consider the function f, where f(x) = (x+1)²"

Or instead, "Let f(x) := (x+1)² ≡ x² + 2x + 1."

:= and ≡ are two different things.

Why did the vector cross the road?

It wanted to be normal.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,771

HI mathsyperson;

Yes, I agree. I wasn't agreeing with the show. Your clarification did make the point clearer to me.

Thanks.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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**Ricky****Moderator**- Registered: 2005-12-04
- Posts: 3,791

And there was a slight mistake on the show.

It all depends on which leaf you choose, but the standard one is to make the value pi.

The mistake that I was more annoyed at was when the show said that ≡ meant "equal by definition"

I've seen this used by a few professors. I don't see anything wrong with it. Different people take symbols to mean different things.

"In the real world, this would be a problem. But in mathematics, we can just define a place where this problem doesn't exist. So we'll go ahead and do that now..."

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**davidbod****Member**- Registered: 2009-08-13
- Posts: 1

mathsyperson wrote:

The mistake that I was more annoyed at was when the show said that ≡ meant "equal by definition".

During my maths degree I found that different lecturers, books and countries didn't have a standard for this (as http://en.wikipedia.org/wiki/Table_of_mathematical_symbols shows).

As for (2n+1)pi, I guess this is true but idea is that the team are looking for the connection between the clues so the answer they should give is that they are all things that *can equal* pi.

I'm glad you're watching the show. I do my best to give maths questins a fair crack of the whip as I feel it's a subject that's under-represented (or, worse, badly represented) in other quiz shows.

Kind regards,

David

OC Question Setter/Editor

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 104,771

Hi davidbod;

Great that you noticed this forum.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**

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