[net.math] -1 = 1, and 1 = 2 'proofs'

lvc@cbscd5.UUCP (09/09/83)

Here is 'proof' that -1 = 1 :

-1 = -1  =>
-1/1 = 1/-1  =>
sqrt(-1/1) = sqrt(1/-1)  =>	(sqrt is the square root operation here)
sqrt(-1)/sqrt(1) = sqrt(1)/sqrt(-1)  =>
sqrt(-1)*sqrt(-1) = sqrt(1)*sqrt(1)  =>
-1 = 1

And one for you calculus fans :

x^2 =  x + x + ... + x	(x times)

differentiate both sides with respect to x

2*x = 1 + 1 + ... + 1	(x times)
2*x = x			(divide by x)
2 = 1 

Larry Cipriani
cbosgd!cbscd5!lvc

leimkuhl@uiuccsb.UUCP (09/12/83)

#R:cbscd5:-55100:uiuccsb:9700005:000:613
uiuccsb!leimkuhl    Sep 11 19:27:00 1983


The proof that -1=1 is interesting since it points up the fact that the sqrt
function for positive reals is NOT like the complex square root.  In 
general, sqrt(x/y)=-sqrt(x)/sqrt(y) if x/y<0, x,y real.  One should use caution 
when applying results derived  in first year algebra courses before being  
acquainted with the complex domain.

In this case,	(1**(1/2))/((-1)**(1/2)) = 1/i = -i,
     while	(1/(-1))**(1/2) =(-1)**(1/2) = i

    so the statement sqrt(1/-1)=sqrt(1)/sqrt(-1) is false.

The second "paradox" is really dumb.  First you assume x is an integer, then
try to use real calculus.  Brilliant.

john@hp-pcd.UUCP (09/14/83)

#R:cbscd5:-55100:hp-pcd:6100003:000:314
hp-pcd!john    Sep 13 09:43:00 1983

Regarding the Calculus Proof:


  The equality x^2 = x+x+x...+x ( X times ) is only true for one value
  of x. Once you pick x you get a parabola that intersects a line at
  that value of x. To imply that because they intersect that they must
  have the same slope is wrong.


John Eaton


hplabs!hp-pcd!john