## #math - Tue 20 Feb 2007 between 22:12 and 22:32

### NY Lost Funds

 JIMJONESBALLIN anubiss, use brackets for open intervals.(5, +infty) anubiss sorryk me22 "anubiss> but if the domain is ok on the denominator, it wil be ok on the numerator for sure..." <-- not necessarily. Sqrt[x]/(|x|+1) the denominator is "good" everywhere, but the numerator isn't.so the domain is [0,inf) despite the denominator being defined for all |R anubiss kis it possible to calculate the derivative of an absolute function ^? me22 not at the "corner" anubiss complicate stuff me22 you just do the 2 parts separately anubiss then id write +- me22 d|x|/dx = { 1 for x >0, -1 for x <0 } anubiss is the use of the conjugate is ok? me22 ? anubiss say i want to calculate a limitlim x->1 (sqrt(x) - 1 ) / (x-1)i would do ihope My simple set theory has one axiom. anubiss lim x->1 (sqrt(x) - 1 ) / (x-1) * (sqrt(x) +1) / (sqrt(x) +1) ihope Comprehension: given a predicate on sets, there is a set containing exactly those sets matching the predicate iff the predicate doesn't match as many sets as p(x) = T does.Of course, you might want to add more axioms to it, like one guaranteeing the existance of sets.This one axiom doesn't guarantee any. __mikem does anyone know why applying the rische integration algorythm on tan x doesn't give ln(sec x) Kasadkad __mikem: What does it give? __mikem ln(some long expression that definitely does NOT equal sec x) Kasadkad You sure it doesn't? ihope % Integrate[Tan[x]] mbot ihope:Integrate::argmu: Integrate called with 1 argument; 2 or more arguments are expected.Integrate[Tan[x]] ihope Well, that sure didn't give Log[Sec[x]] :-P diseaser is there an easy algebraic rule for factoring something like: x^4 - 1 ? me22 ihope : you forgot the ,x __mikem log(sin(2*x)^2+cos(2*x)^2+2*cos(2*x)+1)/2 this is what maxima got me22 diseaser : difference of squares ihope My guess is this Rische integration algorithm isn't plain old integral. me22 anubiss : that's not a conjugate. diseaser me22: cool thanks