The Other Questions Thread

[kira]

Is there a math genius here?

What would the general algebraic formula be for the following chart?

S D Difference (from smaller to next larger)

3 0
4 2 2
5 5 3
6 9 4
7 14 5
8 20 6
9 27 7
10 35 8


S= the number of sides of a polygon
D= the number of diagonals between points of the polygon

Difference- the pattern found between smaller polygon and next larger polygon

So the explanation would be something like: For every side or point added to the polygon, the difference in the number of diagonals increases by one...

I cant get any farther than that and I am trying to articulate the general formula that would explain it somewhat like this: D= S blah blah blah.

This is from the homework of a 10 year old- the formula is not needed for the homework, just for my brain...

It took 2 adults, 1 ten year old and 1 seven year old to get that far. And to think, I used to get straight A's in math.

[justine]

According to me the relation between D and S is:

D = sum (i=2->S-2) i

a.k.a.



-> if you want another way of representing this, i think this page might help: http://en.wikipedia.org/wiki/Arithmetic_progression with a1=2; an=S-2

[kira]

D = sum (i=2->S-2) i

Thank you

Ok- so that is if you are explaining the difference of increase in diagonals.

my brain understands it better as:
given that i=2
Difference= (i-(S-2))+i

But now:

What about if you are solving for the number of diagonals for any given polygon...

D= diagonal in this case.

sorry that was not clear, that is more of what I am looking for...

[Real Real]

Diagonals = ((sides-3)(sides))/2, I think

[kira]

Diagonals = ((sides-3)(sides))/2, I think

Yes that is it:

given that i=3 and s= the number of sides for any given polygon
D= ((s-i)(s))/2

I tested it and it works!!!!!

Thanks guys for helping my brain work today. Surprisingly the ten year old started to say something like that this afternoon and stopped because he got frustrated...we all got frustrated and never pursued it further...

Thank you

[airboyair]

math is sexy!

[kira]

Can someone please tell me how to embed things into a post? I copy and paste and it does not work. I am very good at this thing called a computer, but for some reason embedding does not work for me.


(This should be renamed Kira's Questions Thread )

[Avantster]

What do you want to embed? Say, a youtube video?

[kira]

yes. i copy and paste the embed part on youtube and it never works...

[Avantster]

take the last part of the URL of the youtube video, for example,

http://au.youtube.com/watch?v=pFM-xRKbSec

copy and paste, then simply enclose it in square bracket 'youtube' tags.

(youtube)[COLOR=black]pFM-xRKbSec[/COLOR](/youtube)

[kira]

testing...

[kira]

Thank you Avanster.

[Fade to Black]

math is sexy!

it is

beauty, love, chance, fate, history, time, the infinite and immortal can all be found in the sands of mathematics.

[Avantster]

you can be my good deed for the day, kira.