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#303 Re: This is Cool » Interesting identity » 2006-08-03 05:30:14

It's very simple. And yes, it has connection to the d(x) and many more NT functions
I'll give you a hint: investigate the function:

#304 Re: This is Cool » Interesting identity » 2006-08-03 04:04:03

Ricky wrote:

Maybe I did my addition wrong, but:

3/2???
Nooo...


The function floor is always integer, so you can't get rational result.
And yes, iff.

#305 This is Cool » Interesting identity » 2006-08-02 18:38:55

krassi_holmz
Replies: 7

Prove that n is prime only and only when:

Expand the divisors and sum-of-divisors fuction as sums, which involve the floor function.

Make a function that using floors finds the i-th digit in the representation of n (for example demical representation)

What is the connection between the sum-of-digits function and the standard in the numberic theory

?

#309 Re: This is Cool » Perfect Squares forming some kind of wave » 2006-08-02 09:52:22

I have played for a while with mathematica, and I founded interesting patterns.
The code:

ToCoords[x_][c_] := {Floor[c/x], c - x Floor[c/x]};
SqueezedDotPlot[x_, list_, ops___] := Show[Graphics[Point /@ (ToCoords[x] /@ list)], ops];
SqueezedLinePlot[x_, list_, ops___] := Show[Graphics[Line[ToCoords[x] /@ list]], ops];

Here I will actually use only the first plotting function.

Picture 1: this is the actual square function.

SqueezedDotPlot[10, Range[100]^2]

Picture 2: If you use irrational numbers, there can be interestiong results.

SqueezedDotPlot[4, Range[1000]^Sqrt[2]]

Picture 3: But for most of the numbers, you will get the ordinary noise.

SqueezedDotPlot[Sqrt[10], Range[10000]^3]

Picture 4: Some non-trivial structure

SqueezedDotPlot[Sqrt[2], Range[10000]^2]

Picture 5: The previous zoomed

SqueezedDotPlot[Sqrt[2], Range[1000]^2]

Picture 6: Noise again, but different from the ordinary.

SqueezedDotPlot[3, Range[10000]^1.5]

Picture 7: And what if the exponent is smaller than 1?

SqueezedDotPlot[2, Range[10000]^0.9]

Picture 8: interesting...

SqueezedDotPlot[1, Range[10000]^0.99]

Picture 9: What a wave!

SqueezedDotPlot[2, Range[10000]^0.999]

Picture 10: this is beautiful!!!

SqueezedDotPlot[0.1, Range[10000]^0.5]

#314 Re: This is Cool » imaginary numbers » 2006-08-02 07:08:56

ben wrote:

This simply means that an equality like...I dunno....x² + 2 = 0 has no  solution in R. This is found in C (it's 2i, by the way)

Not only 2i.
Try -2i smile

#315 Re: Help Me ! » Riemann hypothesis » 2006-08-02 06:02:41

Ricky wrote:

Wikipedia provides great reference for information.  But it really only makes sense once you understand the topic.  Don't get me wrong, it may help.  But you are better off looking for a book or site which is meant to teach.

Yes. You're right.
I like wikipedia, because i understand most of what i need.
someone may not.

#316 Re: Help Me ! » Riemann hypothesis » 2006-08-02 04:32:23

And I think Wikipedia is a place where you can understand complicated maths.
If you don't know something (or don't understand it), there a great chance to understand it using Wiki.
Here's a wiki link for the riemann hyp:
http://en.wikipedia.org/wiki/Riemann_hypothesis

#317 Re: Help Me ! » Riemann hypothesis » 2006-08-02 04:26:33

Ricky wrote:

1.  Prove that if a divides c and b divides c, then ab divides c.

4|16 && 8|16 ,but 32 !| 16.
It's :
(a|c && b|c) =>gcd(a,b)|c.

For seven:
The topic is interesting. I think you're brave for posting it. I was not able to read your first posts, because they are DELETED!!! sad

You were asking for a statement, which cannot be proved with some set of axioms and which is true.
Here you're wrong. The "validality" of an statement depends on the set of axioms. There don't exist an universally true statemet, which is true for every set of axioms. So, if an statement A is unprovable over a set of axioms {X,Y,...,Z}, we can assume that it's true or it's false. If we assume that it's true, we are getting the new system: {X,Y,...,Z,A}, in which the statement is provable to be true.
But if we assume that A is false, over the set {X,Y,...,Z,!A}, A is provable to be false.

I hope you to understand.

#318 Re: Help Me ! » Wanted ... a function » 2006-08-02 01:23:04

It must involve the factorials.
I can find limits for this functions (m(x)<=f(x)<=M(x) for every x), and thus some asymptotic relations.
But I want the exact function.

#319 Re: Help Me ! » integrating sqrt(1-x^2) » 2006-07-23 20:30:15

The arcsin() function is commonly used for integration.

#321 Re: Help Me ! » formula or solution to solve this problem. » 2006-07-23 03:19:55

And one last note-strictly, fractional number of minutes won't be allowed, because we define the function (r) as a sum, and thus, it's only for integers (I'm not saying that it can't be defined over R, as we have done, I'm saying that in this case it should be defined only for integers (because we have drops, not stream))

#322 Re: Help Me ! » Plzplzplzplz help me with these problems! » 2006-07-23 03:13:31

luca-deltodesco wrote:

Q1 doesnt really make any sense
Q2

circumference of circle = 2πr
so youre rope is stretched half way around, πr  (π = pi = 3.141592653...bladibla)

but again, unsolvable, because you havnt told use what the radius of the cylinder is.

Abother person which thinks like me.

#323 Re: Help Me ! » solving exponents manually » 2006-07-23 03:11:15

luca-deltodesco wrote:

well. you cant.. not unless its obvious

like what is 2^3, 2*2=4, *2 = 8
or 4^0.5 = 2
27^(2/3) = 9 -> 27^1/3 = cube root, = 3, squared = 9

Yes.
For example, 2^93=9903520314283042199192993792, which is very close to 10^...
But there's another problem-you can't practically use the above, because you must know fast way to evaluate 2^k for every positive integer k<93

#324 Re: Help Me ! » solving exponents manually » 2006-07-23 03:03:49

For example, non-presice result for 2^59:
2^10=1024>10^3;
2^3=8<10;



So 2^59 is between 5*10^17 and 4*10^19, and actually is 5 10^18

With choosing different numbers, you may get more accurate results.

#325 Re: Help Me ! » formula or solution to solve this problem. » 2006-07-23 01:55:28

You are right... - but the answer is a little bigger than 7 seconds, because in the 7th second, there will be 127 drops in the glass, but there must be 127.5, so half a drop must fall, to reach the half of the glass, so the time to full the half of the glass is bigger than 7 seconds with the time of falling of half a drop, which is really small.

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