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#301 Re: Coder's Corner » Best Language to Learn? » 2007-08-23 14:25:28

When I type:

vim hello_world.cpp

I get

bash: vim: command not found

#302 Re: Help Me ! » Simplify expression Math » 2007-08-23 13:17:11

I just googled exponents rules and this is the first one I got:

http://www.purplemath.com/modules/exponent.htm

about halfway down you can see:

Their explanation is pretty good, but if you don't believe it, check out the wiki: http://en.wikipedia.org/wiki/Exponentiation (scroll down to "Identities and properties")

#303 Re: Coder's Corner » Best Language to Learn? » 2007-08-23 08:47:11

I found it free http://newdata.box.sk/bx/c/ but I hate reading online, so I ordered a real cheap one off of amazon. Thanks.

#304 Re: Coder's Corner » Best Language to Learn? » 2007-08-23 07:54:47

Wow, you guys are great, thanks. Cygwin is 86% downloaded now.

I'm going to go google "Teach yourself C++ in 21 days" now, see if I can't find an (affordable) copy somewhere. (I agree fat books are better.)

#305 Re: Coder's Corner » Best Language to Learn? » 2007-08-23 07:26:57

Honestly: I didn't understand most of that. I'm just going to grab onto "I'd recommend getting cygwin" and download that. After that I'll take it step by step. Hopefully things will start to make sense as time goes on.

Any helpful advise to get me going would be great of course.

Thanks for the starting point.

#306 Re: Help Me ! » relearning some Geometry, help on a problem » 2007-08-23 06:23:19

a = x
b = 2x
c = 10

EDIT:

AHHH, mikau beat me.

#308 Re: Dark Discussions at Cafe Infinity » molding a polynomial » 2007-08-23 03:59:11

I think this is a polynomial...

points (a,A);(b,B);(c,C)

You can see how at point (a,A) the right two terms collapse to 0 and the left term collapses to A. This is called the Langrangian interpolation and I got it out of a book named "Meta Math" by Gregory Chaitin.

It's easy (but a little tedious) to add more points on to this.

#309 Re: Coder's Corner » Best Language to Learn? » 2007-08-23 03:37:48

I guess my next question is: how would I go about that? In Flash i just write the code, then run my game to test it. What do I need to buy/download to write the code? Any books or free online tutorials that you could recommend?

Thanks!

#310 Re: Help Me ! » complex number » 2007-08-23 03:33:57

.

So, when does i^m = 1? When m = 4k (k is an integer)

#311 Coder's Corner » Best Language to Learn? » 2007-08-22 15:50:07

bossk171
Replies: 35

I know ActionScript (For Macromedia Flash) fairly well (enough to make cheesy games) but the consensus seems to be that it's not a very good programming language (lack of versatility maybe?)

So I'd like to learn a new one. The question is: what should learn? Java, C++, something else? And how would I go about doing that?

P.S. Is there a difference between C and C++?

#312 Re: Help Me ! » Mobius Strip: 2D or 3D? » 2007-08-22 01:50:36

A 2D sphere doesn't make much sense to me, if it were 2D, why do we need 3D to graph it (x,y,z)?

#313 Re: Help Me ! » Mobius Strip: 2D or 3D? » 2007-08-21 12:22:15

When we discuss a sphere, are we discussing a hollow ball with infinitely thin wall that fits the equation x² + y² + z² = r² or is this some other definition that topology uses?

If it's the former,then a sphere must also be a 2D surface, as is a Klein bottle, no?

#314 Help Me ! » Mobius Strip: 2D or 3D? » 2007-08-20 06:59:50

bossk171
Replies: 15

Well my question is pretty well stated in the subject line.

The argument for it being 2D is that it is a strip, and has no depth, but that doesn't seem right, you can't represent it two dimensionally, you need three dimensions. So what's the deal? 2D or 3D?

#315 Re: Help Me ! » Continued Fraction » 2007-08-19 04:40:17

That was kinda stupid (Curse you conjugates!) but I still think it's wrong, I thought that continued fractions must have a 1 in the numerator, doesn't having 28 mess it up?

#316 Re: Help Me ! » Continued Fraction » 2007-08-19 04:22:51

Well, there definitely seems to be something wrong. I guess you can't have a number other than 1 in the numerator. Anyone want to step in on this?

#317 Re: Help Me ! » Continued Fraction » 2007-08-19 04:08:50

I'm a little shaky on this, but you're starting with:

Just to make things easy (for me), I'm going to do 3 - sqrt(29) first. After we both get the process down, we can do it with the 5.

we know that:

If you don't believe me, just foil. Now dividing through by (sqrt(29) + 1) we get:

adding 1...

And sow for the Stoke of genius. If we know that the above identity is true (which I don't see any reason why it shouldn't) then we can substitute the sqrt(29) on the right with the right of the equation, allow me to show you:

Sweet, let's do it again. (PS sorry LaTeX is making it shrink, and I don't now how to stop it. If any mods want to jump in and fix my formating problem, pleas do.)

And again and again and again...

Ok, I'm going to take a break, I'll be back to finish this up.

EDIT: changed all the 30s to 28s, thanks mathsyperson

#318 Re: Puzzles and Games » The Prisoners and the Cards » 2007-08-10 14:17:29

Are we going to get an answer to this? It's really driving me nuts...

#319 Euler Avenue » complex numbers » 2007-08-10 04:59:21

bossk171
Replies: 0

This is something that's been bothering me for some time, and I thought starting a post on in might help me out. I'm not posting it in the "Help Me" forum, because instead of a question, I was hoping for an open dialog. If some one feels this is the wrong place, then pleas move it to "Help Me."

This is as far as I've gotten:

From that:

That said:

Also:

Which shows:

With a similar method (that is kind of tedious to do out) I found:

I get how to find the kth root of any imaginary number, but I can't make a general rule, I have to do each out by hand.

Using Taylor series I can show :

And from there I think I get k^i, but only if k is a real number.

which leaves me with the following questions:

That last one is a calculator answer, but why?

Any other I properties would be fun to see, so if anyone else has something to offer, please, I'd like to learn as much as I can about complex numbers.

#320 Re: Help Me ! » Distance » 2007-08-09 16:26:34

6 miles per hour = 6 miles per 60 minutes = .1 miles per minute.

So if she went one mile, it took 10 minutes. 90 - 10 = 80, so she had 80 minutes left to walk.

Some how that doesn't seem right...

#321 Re: Help Me ! » Integers » 2007-08-09 16:16:25

Well I don't know how to type the house, so I'm just going to replace the house with Xi, because I think the uppercase xi looks pretty cool.

So:

and

Then what is

Well, first resolve the the parentheses,

Now we resolve the other part:

At least that's how I would do it.

#322 Re: Help Me ! » find x » 2007-08-04 16:32:17

Graphing it shows that -2 is also a value.

#323 Re: Help Me ! » Need Help With One Question » 2007-08-03 17:17:21

12334545 wrote:

Please help me with this 3-part question (Differential Calculus:Rules for differentiation):

Q1) Find the coordinates of the points on the curve y=x²-5x+6 at which the tangent:
A) makes an angle of 45 degrees with the X-axis.
B) is parallel to the line with the equation 3x+y-4=0
C) is perpendicular to the line with the equation 2y-x+3=0

Thanks in advance

Well, as a rule whenever I see "at which the tangent" I find y'

y=x²-5x+6
y'=2x - 5

When a line makes an angle of 45 degrees with the x axis it has a slope of 1 (tan45 = 1)

so y' must be 1

2x - 5 =1
x = 3

plugging that into the original question we get that y = (3)² -5(3) +6 = 0

so A) (3,0)

B) the line 3x+y-4 = 0 or

y = -3x + 4

has a slope of -3. Now repeat the above steps:

y' = -3 = 2x - 5

x=1

and

y = 2

B) (1,2)

The line 2y-x+3=0 or (y = .5x - 1.5)

The slope of a perpendicular is the opposite reciprocal so y' = -2

Blah, blah, blah and so on.

C) (1.5,.75)

#324 Re: Help Me ! » Differentiation- help =[ » 2007-07-30 15:17:51

first, find the y'(x) and y''(x)



So...


solving y''(1) for a we get

pugging that into y'(2) and solving for a we get:

#325 Re: This is Cool » Wooden 3-D graph » 2007-07-30 15:05:36

Thanks for the positive feedback, I've been thinking I'll do a z = x^2 + y^2 (looks sorta like a bowl) next, then maybe z = x*sin(y).

Any other curves that might look cool? (is it still a "curve" if it's in 3-D?)

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