Shadow

Sure thing Thanks. I hope someone can help, cause I'm afraid we can't go much further until then...

Hi all, I put this in Applied Mathematics because I'm going to apply this in real life. I'll let you in on some background so you know why I'm asking. Me and my friend are building a hookah. Since were artistic maniacs who are creatively anti-talented, we want the water jar to be in a shape of an incomplete rhombicuboctahedron. The "incomplete" part is where this gets a little complicated. Since we can't levitate our hookah, and one of us holding it while the other one smokes is out of the question, we need it to be steady of course. So the actual shape of our hookah water jar will be as follows: Take a normal rhombicuboctahedron. It's basically made of an Octagonal Prism, and then those two "things" attached above and below. The "things" are the part where, going around the rhombicuboctahedron, you would see a square, then a triangle, then a square and so on. And theres a square on the very top and bottom. To put it plainly; take away the Octagonal Prism, and what's left is what I'm talking about. Now, take away one of those "things" and put the rhombicuboctahedron back together. You kinda get half a rhombicuboctahedron, but not quite. This is the shape our water jar is supposed to have. My problem lies in the area and volume of this incomplete rhombicuboctahedron. I know the equation for the area of a normal rhombicuboctahedron, but I don't know how it's formed (as in the equation) so I can't edit it to fit my needs with our water jar shape. The same thing goes for volume. Could someone please tell me how the equation is formed, so I can make my own, or maybe even post the equation itself? Thx EDIT: Okay I just found out that the two "things" I was trying to describe are "square cupolae". Love you wiki :-*

The answer to your third question is in Riogho's avatar By "Absolute low", do you mean "Absolute Zero" as in 0 K? if so, check here for what I guess would be the "Absolute High" However, the generally accepted "Absolute Temperature" is called the Planck Temperature and has a value of [math]T_P = \frac{m_P c^2}{k} = \sqrt{\frac{\hbar c^5}{G k^2}} = 1.41679(11) * 10^{32} K[/math] Where: [math]mP[/math] is the Planck mass [math]c[/math] is the speed of light in a vacuum [math]\hbar[/math] is the reduced Planck constant (or Dirac's constant) [math]k[/math] is the Boltzmann constant [math]G[/math] is the gravitational constant The two digits between the parentheses denote the uncertainty (standard deviation) in the last two digits of the value. All this is quoted from Wikipedia.

Okay, one more question; I tried out the %g double. And it works when I predefine the value of the variable, but not when I use scanf(). For example: int main() { double value; value=1; printf("%g milimeters is %g Astronomical Units. Wondering how far the Sun is, eh?\n", value, 6.68458134*value*pow(10,-15)); return 0; } That works. However this: int main() { double value; printf("Enter milimeters:"); scanf("%g", &value); printf("%g milimeters is %g Astronomical Units. Wondering how far the Sun is, eh?\n", value, 6.68458134*value*pow(10,-15)); return 0; doesn't work. Can anyone help? Thx

True.... Okie, thanks ;-)

Hey, never even knew something like that existed xD Thanks ;-) A follow up question though, if I just use "%e" or "%g" by itself, without adding the "x.x" part, does it still display the whole number? Because that's the problem I would run into using float. Since float is I think an 8 byte variable I think, instead of say 0.000000000000000006684 it would just show 0.000000

Okay, first off, I'm just a little above complete newbie concerning C. I tried to learn it and got as far as pointers. Those I could not understand, no matter which tutorial I tried. So if anyone could propose a quality one, that would be great. But that's not the reason I'm writing this. I've been on-off working on this primitive program that would convert given units to given units. Length, weight, time, temperature, all of those. And a problem has arisen right at the beginning. My problem lies in converting small units, such as millimeters, to big length units, such as AU's or Light years. To even get the program to display such big numbers (as in the equivalent of one millimeter in Astronomical Units) I had to use: long double amount; I have really now idea on how precisely it works, specifically the placeholder for it; I just copied the largest variable type I found from the net Anyway, I have a test program where I test out a given part of the code if I need to, so I don't have to compile the whole program, especially when it's not finished. Here's the source of that program: #include <stdio.h> #include <math.h> long double m_ft(long double meter) { long double foot; foot=meter*3.2808399; return foot; } int main() { long double value; printf("Enter milimeters:"); scanf("%Lf", &value); printf("%3Lf milimeters is %.25Lf Astronomical Units. Wondering how far the Sun is, eh?\n", value, 6.68458134*value*pow(10,-15)); return 0; } Anyway, my problem: While the program will display the value, it will be something like "1.0000000000000000 mm = 0.00000000000000000xx AU's". And what's more, I use the variable "amount" (in this program "value") in all the conversions, so I would get things like "1.00000000000000000000 meter = x.xxxx00000000000000000 feet". Now, I want to get rid of the unnecessary digits. It would suffice if someone would help me get rid of the 0 where they are really not necessary, as in the underlined example above. However, if someone where willing, I could use a better solution: How can I make my program, instead of displaying all these long numbers, display something like [math]1 mm=6.68458134*10^{-15} AU's[/math] I know that I'd probably have to specify how big the numbers should be for the program to start displaying them in this format, since I obviously don't want to have stuff like [math]1 mm=1*10^0 mm's[/math], so you'd have to explain all that theory to me. Thanks to anyone who helps, Shadow

Still, you've got the fact that there are stars/galaxies there, although few in numbers. But they're there, and there's nothing wrong with them. I'm jumping to conclusions here, but I would think a connection to another universe, especially one that had completely different physical laws etc., would be a little bit more "stormy". And I certainly wouldn't expect to have stars, galaxies, or any kind of stable matter in the midst of such a gateway...

I see. Okay, thanks all ;-)

Well, how about density?

I see....thanks Mr. Skeptic. Now, for my next question, what is it's exact mass? Or does it vary with the type of material being burned? Or do we even know for that matter?

What I'm asking is, how is it that fire, which is matter as far as I can tell, has no weight, as in gravity having no effect on it. So yes, I'm also asking if it has any mass, or anything that would make it "heavy". Cause, as far as I know, photons are the only particles that have a mass of zero....so how does fire, or plasma in general, fit into all this?

So, that would mean, disregarding burns etc., that if I had a stick weighing, I don't know, half a kilo or something, and a 10 km high flame on it, I could still pick it up?

Well, the title speaks for itself really. This is a reaction to a post made some time ago about what element fire was. Well, it's plasma. But how much does it weight? Or, to be more precise, what is it's density? How do you measure it? If it even has a density, does that mean that when you blow at a candle and the flame gets smaller, it's density increases? Or does the energy somehow dissipates? Thanks in advance for any and all answers.

Yeah, that makes sense....well, thanks all !! :-) I know where to come now if my math teacher again has no idea what I'm talking about

Wasn't that how Pi was originally discovered ? but anyway, thanks, both of you Another question, is it possible to have a circle with a rational circumference and diameter ?

Hello all, Well, this is my first post on this forum. I decided to find a forum like this since the questions I'm about to ask have been bugging me for some time now. Please note though, that I'm only 15 years old (just entered High School a month ago ) meaning that I'm probably missing something that may seem completely elementary to you University Professor's ;-) So excuse my ignorance Now, we all know that Pi is irrational, meaning that it can never be precise. That's also why we can never measure the exact circumference/area of a circle/sphere/whatever. My imagination is still a little limited, and my head usually hurts, when I try to think in 3D, so I'll stick to plain old "flats". My question begins here: Imagine we took a piece of rope/string or something, measuring exactly x meters, made it into a perfect circle, and then attempted to calculate it's circumference with Pi (let's assume that the diameter of the circle would be a rational number). While the circumference would still be exactly x meters, Pi would be trying to convince us that the circumference was around zero point something-something-something x. Because it's irrational of course. Now, if we did it the other way around. If we had a circle that according to Pi had a circumference of y, while the actual circumference was z (y=zero point something-something-something z). We took the circle apart, forming a straight line from it in the process, and measured it's length. We would then find out that the circumference of the circle was actually z, while Pi was telling us that it was y, or zero point something-something-something z. The question: Why don't we measure the circumference of circles like this? And also, how is it possible that Pi is irrational? If what I'm saying is not trash, we should be able to compute the circumference of a circle precisely this way, so that means we should be able to compute Pi precisely. This means that I'm wrong somewhere; where? Another thing, is it possible to draw Pi similarly to the way we draw for example [math]\sqrt18[/math] ? (-> We make a right-angle triangle a,b,c, where c is the hypotenuse and a,b=3 [by the way, what is this process called?]. Whatever it's called, how is it possible to make an irrational number (=infinite number of decimal places) into a line that has a beginning and an end? I know I'd never be able to make a precise [math]\sqrt18[/math] line with a ruler and a pencil, but "virtually" speaking...) I know I'm missing something here, I just don't know what. When I asked my math teacher, she didn't have an answer, so she told me I was way to curious for my age. So I've come here Thanks all, Shadow PS.: Brilliant forum you've got here admins!! You should be proud ;-)