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Homework Help: Exponential rate problem

  1. Sep 14, 2008 #1
    first i had to show solve x′=sin(x) to get t=ln|(csc(x₀)+cot(x₀))/(csc(x)+cot(x))|

    i did that.

    next i need to show that for x₀=(π/4) you can solve x=2arctan(((e^{t})/(1+√2)))

    what i've done so far is


    and haven't been able to get any further. is this on the right track? how do i proceed?

    and finally i need to show that x(t)→pi as t→∞.

    the hint i've gotten is that it involves l'hopital's rule and maybe the equation

    lim t->inf (k/(1+(k/x0 - 1)e^(-mt)-k))/e^(-mt)

    i have no idea what this equation means or how it relates. anyone know?

    thanks a million
  2. jcsd
  3. Sep 14, 2008 #2


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    To simplify there's a trig identity that says arccot(a/2)=csc(a)+cot(a). For the limit, just look at a graph of arctan.
  4. Sep 14, 2008 #3
    sweet. that saved me several hours of pounding my head.
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