Last Person To Post Here Wins (Part 24)

Original post by Matrix123

Soooo...the value of y has the opposite sign of the value of x? I'm sure that's not technically correct :tongue:

I'll wait to see what Associativity has to say on the matter :u:

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Generally, those double bars would be spoken to be the "modulus" or "mod" of the number (not to be confused with the modulo function, which is something different). So for instance, |x| would be read as "the modulus of x", or lazy (most) mathematicians would speak it to be "mod x". You might also hear this called the "absolute value", means the same.

The definition you gave was right in this context, for real numbers. You can think about it as the "Magnitude" of the number; i.e how big it is, regardless of its sign. So yes, you can define it as follows

{x, for x>=0
|x|= {
{-x. for x<0.

so |-5| = 5. Notice that for x=5 and x=-5, the value of |x| is the same. You can think of this as being because they have the same magnitude, just different signs.

(edited 7 years ago)

Reply 7321

|x| has the shape of graph shown with both the person's hands going straight up, it's basically like drawing y=x, but reflecting everything left of the y axis in the x axis, to get a graph that looks like this: \/ (excuse ascii :smile:

)

The other ones on there you might not have met are cot x (which is 1/tanx), log_a (x) (which is a number such that a^(log_a (x)) = x), and possibly x^2+y^2=a^2 (which is a circle).

(edited 7 years ago)

Reply 7322

Original post by Matrix123

Sorry I can't rate you Matrix, the maths vid is great.

Note, that the last one on your pic isn't actually a function, so they couldn't really include this and call it "Uptown Funktions" :smile:

.

If you like that, you may like (perhaps even find useful) this, and other videos by these people. They're a bit of a novelty, but actually really useful for explaining how sorting algorithms work. Here is the folk dance for the quicksort algorithm.
[video="youtube;ywWBy6J5gz8"]https://www.youtube.com/watch?v=ywWBy6J5gz8[/video]
You'll need an explanation on paper to understand how this works properly, but this is a nice demo.

Reply 7323

Charles III

21

Original post by Associativity

Sorry I can't rate you Matrix, the maths vid is great.

Note, that the last one on your pic isn't actually a function, so they couldn't really include this and call it "Uptown Funktions" :smile:

.

If you like that, you may like (perhaps even find useful) this, and other videos by these people. They're a bit of a novelty, but actually really useful for explaining how sorting algorithms work. Here is the folk dance for the quicksort algorithm.
[video="youtube;ywWBy6J5gz8"]https://www.youtube.com/watch?v=ywWBy6J5gz8[/video]
You'll need an explanation on paper to understand how this works properly, but this is a nice demo.

I'm glad you're chief morale officer :proud:

Reply 7324

Original post by iEthan

I'm glad you're chief morale officer :proud:

How come

Reply 7325

Charles III

21

Original post by Associativity

How come

You're good at boosting morale :bigsmile:

if u let me win I'll give you a cookie

Reply 7328

1682795

16

Original post by bluemadhatter

if u let me win I'll give you a cookie

Deal.

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Reply 7329

Matrix123

Chat Forum Helper, Entertainment Forum Helper

Original post by Associativity

Generally, those double bars would be spoken to be the "modulus" or "mod" of the number (not to be confused with the modulo function, which is something different). So for instance, |x| would be read as "the modulus of x", or lazy (most) mathematicians would speak it to be "mod x". You might also hear this called the "absolute value", means the same.

The definition you gave was right in this context, for real numbers. You can think about it as the "Magnitude" of the number; i.e how big it is, regardless of its sign. So yes, you can define it as follows

{x, for x>=0
|x|= {
{-x. for x<0.

so |-5| = 5. Notice that for x=5 and x=-5, the value of |x| is the same. You can think of this as being because they have the same magnitude, just different signs.

Ohhh OK.
Oooh that's cool! :yep:

thanks for clearing that up

Original post by Associativity

|x| has the shape of graph shown with both the person's hands going straight up, it's basically like drawing y=x, but reflecting everything left of the y axis in the x axis, to get a graph that looks like this: \/ (excuse ascii :smile:

)

The other ones on there you might not have met are cot x (which is 1/tanx), log_a (x) (which is a number such that a^(log_a (x)) = x), and possibly x^2+y^2=a^2 (which is a circle).

Ahhh I understand :biggrin:

I've come across the circle one before

Original post by Associativity

Sorry I can't rate you Matrix, the maths vid is great.

Note, that the last one on your pic isn't actually a function, so they couldn't really include this and call it "Uptown Funktions" :smile:

.

If you like that, you may like (perhaps even find useful) this, and other videos by these people. They're a bit of a novelty, but actually really useful for explaining how sorting algorithms work. Here is the folk dance for the quicksort algorithm.
[video="youtube;ywWBy6J5gz8"]https://www.youtube.com/watch?v=ywWBy6J5gz8[/video]
You'll need an explanation on paper to understand how this works properly, but this is a nice demo.

No worries. Haha I'm glad you liked it :smile:

well, it was rather enjoyable until my teacher played it and tried to get us to do the moves :colonhash:

Ahh that's absolutely unbelievable! Oh well, at least the others are right. Thanks for pointing that out :wink:

Oooh I love the sound of this! I'll watch it at some point today :yep:

I'm learning about quicksort algorithms so I'm sure this will really come in handy :h:

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Reply 7330

AngryJellyfish

Unparseable latex formula:

\begin{equation*}R = [br] [br]\displaystyle{\sum_{i=1}^n (x_i-\bar{x})(y_i- [br] [br]\bar{y})}}{\displaystyle{\left[ [br] [br]\sum_{i=1}^n(x_i-\bar{x})^2 [br] [br]\sum_{i=1}^n(y_i-\bar{y})^2\right]^{1/2}}} [br] [br]\end{equation*}

Reply 7331

Matrix123

Did someone say cookie? :ahee:

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Reply 7332

Matrix123