Math Is Fun Forum

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

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#2 Re: Help Me ! » (Dis)Proof pi = 2 (!) » 2010-08-10 21:33:27

The error lies in your 4th step. All you've done is proven that the arc lengths of a convergent series of paths does not necessarily converge to the arc length of the limit path.

#6 Re: Help Me ! » ampere-maxwell law » 2010-04-12 01:26:43

Recall that the charge (Q) in a cylindrical capacitor is;

Q(t) = C·V(t)

where C is the capacitance and V(t) is the applied voltage. Differentiating, we get the current I(t);

I(t) = C·dV(t)/dt

Hope this helps.

#8 Re: Dark Discussions at Cafe Infinity » Purpose of life???? » 2010-04-10 07:00:18

How do you know what the correct way to interpret the Qur'an is?

#9 Re: Dark Discussions at Cafe Infinity » Purpose of life???? » 2010-04-10 06:29:14

there are people who use it fore good purposes and others for bad purposes....

What do you mean?

#10 Re: Dark Discussions at Cafe Infinity » Purpose of life???? » 2010-04-10 03:45:16

a TRUE muslim can not kill an innocent person.

What is a "TRUE muslim"?

#13 Re: Dark Discussions at Cafe Infinity » Happy Pi Day! » 2010-03-17 04:21:55


#14 Re: Help Me ! » How do I figure this? » 2010-03-09 18:22:45

You'd need more information. It looks like arc AB is bigger than arc BC, but to be sure you'd need annotations.

#15 Re: Help Me ! » Save Me From Failure » 2010-03-03 08:52:26

If you do get your test back, tell me about any questions which you got wrong, and I'll post a video solution of them. smile

#16 Re: Help Me ! » Save Me From Failure » 2010-03-01 19:06:19

Is that okay, misheeru? I can create a video if the solution is still unclear.

#17 Re: Help Me ! » Help me, I am infinite, I am not supposed to be here » 2010-02-28 07:21:08

Please wait. I am raising you to the 0th floor.

(you are now undefined)

#19 Re: Maths Is Fun - Suggestions and Comments » Spelling? » 2010-02-27 21:13:31

Your browser language setting is en-GB

So these are the spellings we will use:

Maths, metre, litre, colour, organisation.

UK is fine. smile

#20 Re: Dark Discussions at Cafe Infinity » Purpose of life???? » 2010-02-27 08:47:16

d1whohatesmath wrote:

the quran tells about ... how the universeworks,the night of power,ect.really,all you need is to sit down and dedicate your time to reading and really understanding what the quran says.

And yet, it's funny how those "predictions" about science are only discovered after the science.

#21 Re: Help Me ! » integration help please » 2010-02-26 07:12:21

And if you're still having trouble, I can make a video on this problem if you like. smile

#22 Re: Help Me ! » Multiplication? » 2010-02-24 08:26:24

Here's a link to a video looking at a multiplication trick;

Unfortunately, it doesn't yet have any annotations... if you can make sense of it without them, great! If not, ask me here. I'll add the annotations later.

#23 Re: Help Me ! » physics questios » 2010-02-23 11:04:01

9) What happens when you split an electron? I heard that, if you took an electron ( say it had a charge of 1 ), and you split it (how would you do this, anyway?), would the two new electrons created (if that is what happens, if not what happens?) have charges of 1/2 and 1/2 respectively?

To my knowledge, you cannot split an electron. At least, not according to the very well established quantum theory of electromagnetism and electrons. As far as current scientific knowledge, the electron is not divisible.

5) Is nothingness possible to exist, or is it simply a phenomenon that cannot exist?

By definition, nothingness can't exist. I'm pretty sure mathematics defines this well as the 'null set'.

1) The universe is expanding, correct? This means that its centre of mass is constantly changing, and the centre of the universe is also constantly changing (well... if the universe is spherical, and was increasing in proportion to a sphere). Is this why our Solar System is moving?

Think of the balloon analogy for a 2-dimensional universe. The universe is on the surface of the balloon, which is expanding. Points on the balloon move away from each other as it expands. Even though the universe is expanding, it doesn't make sense to talk about motion of a centre of mass.

8) Why can't neutronium exist on Earth? Why can't I hold it in my hand?

Neutrons by themselves are unstable and decay into a proton and electron with a half-life of about 15 min. Without protons in the right ratio, as in a nucleus, to stabilize the neutrons, your neutronium will decay away. It's only when there is enough pressure from gravity to prevent this decay that you can have stable neutronium.

#24 Re: Jokes » yo mama jokes » 2010-02-23 08:46:18

The mass of Yo' Mama at rest is approximately equal to that of a neutron star travelling at 1 - 10[sup]-1000[/sup]c.


#25 Re: Help Me ! » how many different colors are there ? » 2010-02-23 08:24:23

Well, there are a number of different answers to this question. A 24-bit RGB computer monitor can simulate 16,777,216 colours. It works like this;

We have three 'columns' -- 0 0 0. We can add any number to these columns, i.e. if we add 127 to the first column, 61 to the second, and 39 to the third, we get 127 61 39. This represents the amount of red, green, and blue respectively. The maximum is actually 255 per column, leaving us with 256 possible combinations per column. To calculate the number of combinations, that is 256³, or, 2[sup]24[/sup], which is 16,777,216.

However, in reality, we know that, of course, 16,777,216 is not the actual number of possible colours. The visible spectrum of light means that we can see wavelengths between 380 and 740 nm (nanometres), hence why there are infinite possibilities; you can have fractional wavelengths. For example, 491.66206782365 nm could be a visible wavelength.

In terms of how many colours a human can perceive? That depends. The perception of colour varies from person to person... the number of different colors that you, as an individual, can distinguish also varies dramatically according to the conditions; it drops to zero in low light conditions, in which only the rod cells of the retina can function, as the cone cells of the retina are required for color vision. So there is no single number that applies to everyone. I believe the estimate is between 1 and 10 million.

[ Also, 0 0 0 isn't always used -- sometimes 00 00 00 - FF FF FF is used (hexadecimal). The number of combinations is still the same, because 00 in hexadecimal is 0, and FF is 255. So there are still 256³ = 16,777,216 combinations. ]

(EDIT: Sentence didn't even make sense. tongue )

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