the tree Posted January 5, 2012 Share Posted January 5, 2012 What's there to think about it? It's a well known equality. Link to comment Share on other sites More sharing options...
The french tourist Posted January 30, 2012 Share Posted January 30, 2012 Could the seeming lack of precision in Pi, be due to our human custom of using decimal notation. For example, if we divide something into 3 parts, each part is then, in decimal notation, an imprecise 0.333333333.... of the original. Those kinds of notations are not imprecise. You can easely prove that 0,33333... = 1/3 or 0,99999...=1 (without any imprecision). For example, let x=0,999999... Then we have 10x=9,99999.... Hence 9x=9 (Writting the soustraction of 10x and x, you can skip the decimal part). Finally x=1. You can do the same with 0,33333... (let y=0,33333... And, at the end, you will find 3y=1. There's no lack of precision in these notations, they're just heavy and useless). Link to comment Share on other sites More sharing options...
John Cuthber Posted January 30, 2012 Share Posted January 30, 2012 (edited) If a proof does not exist (in the ethereally mathematical sense of existence), then technically speaking it would be neither rational nor irrational, I suppose some non-computable numbers fall between the gaps in that sense. I'm fairly sure that a proof always exists for the rationality of any rational number. If it is rational number then it can be expressed as a ratio of two numbers a and b where a and b are integers. So, for any rational number the proof is simple. Find a and b. It may not be practical since it may take an (almost) infinite time. Edited January 30, 2012 by John Cuthber Link to comment Share on other sites More sharing options...
DrRocket Posted January 30, 2012 Share Posted January 30, 2012 I'm fairly sure that a proof always exists for the rationality of any rational number. If it is rational number then it can be expressed as a ratio of two numbers a and b where a and b are integers. So, for any rational number the proof is simple. Find a and b. It may not be practical since it may take an (almost) infinite time. There are numbers for which it is not know whether they are rational or irrational. [math]e + \pi and e \pi[/math] are such numbers. That does not mean that no proof exists, only that no one has found a proof either way thus far. A proof that no proof exists would be a proof of undecidability of the question. No proof of undecidability has been found either. Your suggestion as to a proof won't work. It won't work because if a number is presented as a ratio orf integers, there is nothing left to do, and if it is not so presented you have no test to determine if any given ratio is the number in question -- try your method on [math] e+ \pi[/math] for instance and you will find that you have no way to make a comparison. Note that while we do not know whether [math] e + \pi[/math] or [math] e \pi[/math] are rational, it is known that at most one of them can be rational. The proof is in fact quite simple. Link to comment Share on other sites More sharing options...
*puffy* japanisthebest Posted February 7, 2012 Share Posted February 7, 2012 I know that calculating Pi requires more complex mathematical operations, as we go farther away from the decimal point, I'd ask .. is it true that [math]\pi = \frac{22}{7}[/math] I mean, is it only true for number of digits after the decimal point .. or is it the exact answer ? [math]\pi = \frac{22}{7}[/math] is probably only true for a little bit.. i think.. Link to comment Share on other sites More sharing options...
DrRocket Posted February 7, 2012 Share Posted February 7, 2012 [math]\pi = \frac{22}{7}[/math] is probably only true for a little bit.. i think.. [math]\pi[/math] is irrational, and in fact transcendental. [math]\frac {22}{7}[/math] is manifestly rational. They are never equal. But [math]\frac {22}{7}[/math] is an acceptable approximation to [math]\pi[/math] in some simple applications. Link to comment Share on other sites More sharing options...
ewmon Posted February 24, 2012 Share Posted February 24, 2012 π is the ratio of the circumference of a circle to its diameter, and yet, it is the irrational ratio. Link to comment Share on other sites More sharing options...
D H Posted February 27, 2012 Share Posted February 27, 2012 π is the ratio of the circumference of a circle to its diameter, and yet, it is the irrational ratio. Don't get hung up on the label "irrational". Mathematicians, until recently, were a rather stodgy lot. Look at the names they gave things. Irrational numbers: Numbers that don't make a bit of sense. The symbol preceding 2 in [math]\surd 2[/math], is the surd symbol: Short for absurd. Negative numbers: Things that aren't numbers. Imaginary numbers: Numbers that aren't quite "real". The designation of the real numbers as the real numbers was a back-formation to contrast the numbers that truly are "real" from those that are not. Nowadays mathematicians have embraced the rainbow and they have all kinds of numbers. These more recent inventions tend not have some derogatory label such as irrational, absurd, negative, imaginary, or complex. Instead they are merely given descriptive names such as transfinite numbers, p-adic numbers, quaternions, octonions, etc. Link to comment Share on other sites More sharing options...
swansont Posted February 28, 2012 Share Posted February 28, 2012 ! Moderator Note connector's "pi solved" tangent has been moved http://www.scienceforums.net/topic/64686-pi-solved/ Link to comment Share on other sites More sharing options...
JohnStu Posted February 28, 2012 Share Posted February 28, 2012 It is endless because how you derive pi depend on how much you "zoom in" in the curve. The more accurate and detailed to measure the circumference, the more correct decimal digits. In construction of circles, some architects avoided calculation of pi by simply using a fine brush tied to a stick and span it on the sheet, and viola, a perfect circle. No need to calculate the area. Link to comment Share on other sites More sharing options...
phillip1882 Posted March 1, 2012 Share Posted March 1, 2012 (edited) while pi is indeed transcendental, there are some nice representations of it none the less. one of my personal favorites.... 3 + 1/(7 +1/(15 +1/(31 +1/63.... edit: this is wrong I'm afraid. a much more correct version is... 4/(1 +1/(3 +4/(5 +9/(7 +16/(9 +25/... Edited March 1, 2012 by phillip1882 Link to comment Share on other sites More sharing options...
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