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

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#55976 Re: Help Me ! » Trig » 2009-04-27 01:19:14

Hi ilovealgebra;

You are given

First get the derivative:

Now get the slope m by plugging in -3 in the right hand side

Now get

Now you have

Just plug into the slope tangent formula

simpllfy

#55977 Re: Exercises » Square Roots » 2009-04-27 00:16:34

Hi nurshodiq;

I think that


is the only solution.

Since it factors into:


and both of those terms are greater than 1 for all


must consist of 2 or more primes or two or more composites so

cannot be prime

#55979 Re: Help Me ! » muliple probability » 2009-04-26 04:33:57

Hi mathsyperson;

  Thanks for checking my work, probability is so error prone and so counter intuitive.

#55980 Re: Guestbook » Theoretical Computing » 2009-04-26 02:34:21

Hi dannyv;

   Haven't read that one yet. The first thing I ever saw a random walk used on was getting any element of an inverted matrix without inverting the matrix, thought that was so great.

#55981 Re: Help Me ! » 1=2 proof » 2009-04-25 19:17:53

Hi dreamalot;

   I'm afraid Jane is right about learning correct proofs but if you are determined to see this, here is a link that I know of.
http://en.wikipedia.org/wiki/False_proof

#55982 Re: Help Me ! » muliple probability » 2009-04-25 18:31:24

Hi eclipse;

Looks like a binary tree so you multiply and add:

So there is almost a 19% chance that event won't happen.

or somewhat easier:

#55983 Re: Help Me ! » muliple probability » 2009-04-25 14:30:46

Hi eclipse;

  You would be able to add them if they are independent of each other. If that is what you mean by separate ( they are independent ) then just add. There is a formula for when they aren't independent but you haven't provided enough info for me to use it. You were probably given a Venn diagram, provide me with that info.

#55985 Re: Dark Discussions at Cafe Infinity » The singer Rihanna - Asulted! » 2009-04-25 11:21:31

Sometimes I think, wouldn't be great if they would just transport Hollywood to some other country.

#55986 Re: Guestbook » Theoretical Computing » 2009-04-25 11:11:08

Hi dannyv;

   Random walks are really a powerful and beautiful piece of math. Along with generating functions and graph theory they are the cornerstone of the new discrete approach to mathematics.  I have always been partial to problems 6,7,12,14 on that page.

#55988 Re: Guestbook » Theoretical Computing » 2009-04-24 21:16:22

Hi dannyv and MathsisFun;

    Like those fields, but I am just an untalented amateur in them. I took up computing so that I wouldn't have to do anymore math, but discovered I needed more math than ever before.

   That is generally true with coding. A piece of code starts out pretty, small and readable, but as I add bells and whistles. it turns into a monstrosity. I also like to get the job done. I find the drive to achieve good structure, boring. Just let it rip, is the fun way to program.

#55989 Re: Euler Avenue » Discrete Fourier Transform » 2009-04-24 20:06:07

Hi dannyv;

From my notes I can answer question 2:

If n is of the form 4m then the eigenvalues are:
m+1 eigenvalues that equal 1
m eigenvalues that equal -1
m eigenvalues that equal -i
m-1 eigenvalues that equal i

If n is of the form 4m+1 then the eigenvalues are:
m+1 eigenvalues that equal 1
m eigenvalues that equal -1
m eigenvalues that equal -i
m eigenvalues that equal i

If n is of the form  4m+2 then the eigenvalues are:
m+1 eigenvalues that equal 1
m+1 eigenvalues that equal -1
m     eigenvalues that equal -i
m     eigenvalues that equal i


If n is of the form 4m+3 then the eigenvalues are:
m+1 eigenvalues that equal 1
m+1 eigenvalues that equal -1
m+1 eigenvalues that equal -i
m     eigenvalues that equal i

Unfortunately my notes are sketchy on deriving the characteristic eqtn (your question #1). So do yourself a favor and keep good notes, don't be like me. Try google for DFT and eigenvalues that may turn up an alternate reference.

#55990 Re: Puzzles and Games » Connotations. » 2009-04-24 19:43:48

waistband

clarinet

salmonella

#55991 Re: Euler Avenue » Discrete Fourier Transform » 2009-04-24 12:17:13

Hi dannyv;

  As far as I can remember the eigenvalues for those matrices are taken from the set of the roots of unity, solutions of z^n-1=0 where n is the size of the matrix. I think there is an easy way to determine how many of each by n modulo 4.  I might be mistaken, its been a long time since I have worked with a DFT or FFT. Google will probably provide what you need.

#55992 Re: Exercises » Play with numbers » 2009-04-24 10:34:00

Hi smiyc86;

   Hard to believe but I am familiar with manjyome's stuff. Anyway why should we consider his/her answer. After all it is only a probable answer( 3 out of 5). Berry's idea, underneath manjyome's post is right on the money. I don't have any way at present to firm up manjyome's work. If you do I would like to see it.

#55994 Re: Puzzles and Games » Connotations. » 2009-04-23 19:07:01

Sorry Jane, was bleary eyed. Will try harder.

1 deformation

2 organ

3 cabbage

#55998 Re: Puzzles and Games » Connotations. » 2009-04-22 20:45:48

function

insect

nutritious

#55999 Re: Puzzles and Games » Puzzlers - you can use the "Hide" tag » 2009-04-22 20:24:23

Hi quittyqat;

Now I see it! Is the Thanks for me?

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