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#26 Re: Help Me ! » A cubic... » 2006-01-08 05:21:32

God

Lol.thanks... wow... that looks so complicated lol

#27 Help Me ! » A cubic... » 2006-01-03 15:32:08

God
Replies: 20

Can the cubic 0 = x^3 - x - 1 be solved by means of simple algebra (without the cubic formula)?

#28 Re: This is Cool » Polynomial division, and more » 2006-01-03 15:18:26

God

While you're at it, here are some links to some other polynomial solving stuff...

http://mathworld.wolfram.com/DescartesSignRule.html
http://mathworld.wolfram.com/IntermediateValueTheorem.html

And for fun:
http://mathworld.wolfram.com/NewtonsMethod.html

This is horrible but helpful:

#29 Re: Help Me ! » Greek Letter » 2006-01-03 15:05:05

God

ω - lowercase omega
at least that's how I've seen it

#30 Re: Help Me ! » Help with 3D rotation » 2006-01-01 12:41:46

God

The work seems right, so if you made a mistake, I haven't noticed it. Thanks

#31 Re: Help Me ! » D(x^x) » 2006-01-01 12:38:10

God

I couldn't get it to work and my TI-89 Titanium couldn't either and neither could the wolfram Integrator.

#33 Re: Help Me ! » Help with 3D rotation » 2005-12-30 12:21:44

God

See the problem, to be more specific, is that I can't figure out how to integrate ƒ(x)... esp. the x^x

#35 Re: This is Cool » vector multiplicated by i » 2005-12-30 12:00:20

God

The length (aka. magnitude) of the vector is still it's absolute value.

So for example, if you had a vector <1+i, i-1>, the absolute value of your x component is sqrt(2), the absolute value of your y component is sqrt(2), and so the length of the vector is 2.

#36 Help Me ! » Help with 3D rotation » 2005-12-30 11:33:51

God
Replies: 30

Given the function:
ƒ(x) = e^x-ln(x)-x^x on the interval 1/e <= x <= e

I now have to rotate this around the line x + y = 1

What will be the volume of the solid?

Just for a visual:
function.gif

Thanks

#37 Re: This is Cool » vector multiplicated by i » 2005-12-30 11:25:14

God

So it exists in a complex 4-D coordinate system but only exists at the origin on a 2-D real system where the origin of the vector is (0,0).

#38 Re: This is Cool » Interesting suggestions about floor[x] » 2005-12-30 11:20:30

God

Awesome work!

About the square impulse, I'm sure it can somehow be derived from the equation of a circle, since you can control the endpoints by controling the center and radius.

If you allow limits, it becomes even easier (but totally useless for most practical cases)
The corresponding function g(x) would be represented in the form:
g(x) = lim(n->oo)[((x-a)/b)^n]*ƒ(x)+ƒ(x)
for the interval (a, a+b]

#39 Re: Help Me ! » Area of a circle » 2005-12-28 16:42:30

God

That works, yes, but if r is the principle variable, then 2pi r is a line and pi r^2 is a parabola, so you aren't dealing with a circle, are you?

#40 Re: This is Cool » Interesting suggestions about floor[x] » 2005-12-28 07:31:02

God

cool... how did you come up with that?

#41 Re: This is Cool » Iterated Polynomials » 2005-12-28 07:28:25

God

I would say it is not a polynomial. Apart from the fact that you cannot iterate a polynomial infinitely many times, consider this:

ƒ(x) = x^2

ƒa(0) will always be 0, and ƒa(1) and ƒa(-1) will always be 1. For all x not equal to 0 such that |x| < 1, ƒa(x) approaches 0 as a approaches ∞, and for all other numbers, ƒa(x) tends to ∞ as a tends to ∞ - that is, it does not exist. So what you're left with in a limiting case is a discontinuous (and nonexistent) function defined only for the domain [-1, 1].

#42 Re: This is Cool » One divided by Infinity » 2005-12-28 06:57:03

God

Infinity is meaninglessly large, so there's really no poing in wondering what 1/infinity is unless you're dealing in terms of limits. You can't divide by infinity because it's not a number. Just like I can't divide 1 by an elephant or an egg.

#43 Re: Help Me ! » High School Student needs your help please... » 2005-12-28 06:46:30

God

1. General form of a parabola equation is: (y-k)=a*(x-h)^2 where (h,k) is the vertex and a is a scale factor.

That gives y+1 = a*(x+4)^2

Since (0,-5) works for the equation, substitute and solve for a:

-5 + 1 = a*(0+4)^2
-4 = a*16
a = -1/4

so your equation is:

y + 1 = -1/4 * (x+4)^2

2. Let x be one number and (x-10) be the other number...
    So you want to minimize x*(x-10), which is x^2 - 10*x. The lowest point is at the vertex, so the       
    x coordinate of the vertex is one number, and your other number is x-10.
    Vertex occurs at -b/2a = 10/2 = 5, so the two numbers are 5 and -5

#44 Re: Help Me ! » Is there any way to solve this algebraically? » 2005-12-28 06:37:50

God

It is definately true that it only works for 1 and 2, but I guess, being more specific, is it possible to isolate x? As in use algebra to bring the equation down to an x = 1?

#45 Re: Help Me ! » Is there any way to solve this algebraically? » 2005-12-21 22:53:27

God

Yeah I tried logs and changes of bases and etc but it just simplifies to the original equation.

The only answers are x = 1 and x = 2, which can be proved once you do "find" them...

#46 Help Me ! » Is there any way to solve this algebraically? » 2005-12-21 09:27:04

God
Replies: 15

Can this be solved fully algebraically?

2^x = 2x

~ Thanks

#47 Re: Help Me ! » Recurrent relation » 2005-12-21 09:18:57

God

I really didn't get what you were trying to do with that recursive equation sad or else I'd help

#48 Re: This is Cool » 0x∞=-1 ??? » 2005-10-30 13:17:36

God

General comments:

∞ is not a slope. The gradient of a vertical line is not ∞, since one could argue that it is also -∞, which is completely different.

0 x ∞ = -1
2 x 0 x ∞ = -1 x 2
0 x ∞ = -2
-1 = -2
You're right, this is way to complicated for the human mind to comprehend... meep

I'm going to stick to my safe and solid viewpoint that infinity is not a number until someone enlightens me.

#50 Re: Help Me ! » Finding a Cubic Equation from Complex Roots » 2005-10-30 13:05:56

God

Expand:
(x-2)(x-1-i)(x-4-2i)
That should be your answer.

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