gib65 Posted April 29, 2008 Share Posted April 29, 2008 I find fringe mathematics fascinating. There are equations like e^(pi*i) = -1 that boggle my mind and proofs for how 0.999... = 1 that just amaze me. I thought it would be cool to start a thread for people to post proofs/facts/interesting problems in math that warp our common sense notions about how numbers work. I'll start with the proof that .999[bar]=1 (where [bar] denotes an infinite series): x=.999[bar] 10x=9.99[bar] 10x-x=9.99[bar]-.999[bar] 9x=9 x=1 Link to comment Share on other sites More sharing options...
DeanK2 Posted June 19, 2008 Share Posted June 19, 2008 Wiles proof that [math]x^n+y^n=z^n, n>2 --> xyz=0[/math] Lebiniz and his most elegant equation [math]pi/4=1-(1/3)+(1/5)-(1/7)....[/math] Link to comment Share on other sites More sharing options...
the tree Posted June 22, 2008 Share Posted June 22, 2008 As far as calculations for π go, by far the most awesome although completely useless is the Buffon Needle experiment. Link to comment Share on other sites More sharing options...
alan2here Posted July 17, 2008 Share Posted July 17, 2008 e^(pi*i) = -1 Can you move that around so that "pi =" is on the left? There is also a way involving iterative sin of a number that gets pi. Link to comment Share on other sites More sharing options...
Air Posted July 20, 2008 Share Posted July 20, 2008 x=.999[bar] 10x=9.99[bar] 10x-x=9.99[bar]-.999[bar] 9x=9 x=1 An alternative approach (using fractions): [math]\frac13 = 0.33333...[/math] [math]\frac13 \times 3 = (0.33333...) \times 3[/math] [math]1 = 0.99999...[/math] Link to comment Share on other sites More sharing options...
ydoaPs Posted July 20, 2008 Share Posted July 20, 2008 Oh gods......not ANOTHER 0.9999999=1 thread! Link to comment Share on other sites More sharing options...
Air Posted July 21, 2008 Share Posted July 21, 2008 Oh gods......not ANOTHER 0.9999999=1 thread! Hmmm... Not quite. I was just posting an alternative proof. This thread is about (Quoted OP): I thought it would be cool to start a thread for people to post proofs/facts/interesting problems in math that warp our common sense notions about how numbers work. Link to comment Share on other sites More sharing options...
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