#math - Wed 18 Apr 2007 between 02:59 and 00:36

NY Lost Funds



TRWBW?
ConcernedWithSec: go with god
ConcernedWithSechow old are you guys?
thermoplyae19 and getting older every second
TRWBWPuppiesOnAcid: so if they are all 3 different points, and no 2 of them are verticle, than you can compute slope A to B and slope B to C, and they are on the same line if and only if those are equal
PuppiesOnAcid: with me on the 2D case?
PuppiesOnAcidYep
TRWBWPuppiesOnAcid: so now in 3D. well slope=rise/run. where run is change in x and rise is change in y, yes?
PuppiesOnAcid: (that is in 2D that's what slope is)
PuppiesOnAcidyes
TRWBWPuppiesOnAcid: so in 3D you can think of two slopes, slope_y and slope_z. slope_y is (change in y)/(change in x) and slope_z=(change in z)/(change in x)
PuppiesOnAcid: and the 3 points will be collinear if slope_y(A,B)=slope_y(A,C) *and* slope_z(A,B)=slope_z(A,C)
PuppiesOnAcidGot it
TRWBWPuppiesOnAcid: unfortunately, it gets more complicated if any of those (change in x)=0. that's like the verticle case in 2D, but in 3D its worse
PuppiesOnAcidI am pretty sure that is not the case.
TRWBWPuppiesOnAcid: then you are fine
netpro25_anyone know how to find the sum of the series? sum(n=0..oo, (1/(2^n))
TRWBWnetpro25_: it's a geometric series, they should cover that in your book
netpro25_: i could give you the formula, or try to show you where it comes from
netpro25_k i am stuck on the algebra
let me show you
TRWBW?
netpro25_i gave you the wrong problem
hold on
sum(n=0..oo, (1/(2^n) - (1/(3^n))
i got the divided into two sums
TRWBWk
same thing before, it's geometric sums
netpro25_do you plug in oo?
TRWBWthat means a sum of the form a_n=b*r^n
you got 1/2^n=1*(1/2)^n and 1/3^n=1*(1/3)^n
but in either case the formula is b/(1-r)
netpro25_k
i see it
ah i see
thanks trwbw you the man
TRWBWnp
jadenbaneWhat's a quick check to see if teo matricies are similar. detA=detB?
Or do I have to find the eigenvalues of both?
KasadkadThat's a necessary but not sufficient condition

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