Recent content by a_Vatar

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    Sketching a graph that meets given condition

    A continuous function on an interval(in R), should possesses an intermediate value property. That's why it's impossible
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    Non-empty perfect set in R with no rational number

    C'mon, guys. There must be something wrong with this naive construction, otherwise it would be used as an example(on planetmath for instance).
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    Non-empty perfect set in R with no rational number

    Instead of creating a new thread, I decided to just write in here. If we define a set X={p in (0, 1), p in R} and let E = X \ Q. Now, E non-empty(since Q is countable and X is not) and bounded, furthermore, no point of Q is in E. Now what remains to be shown is that if p in E, then p is a...
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    Limit superior (lim sup) of a sequence

    HallsofIvy, I'm studying with Rudin’s Principles of Mathematical Analysis. They define lim sup exactly as sup of a set of all subsequential limits. So let E be a set of all subsequential limits and let x = lim sup(an) = sup(E), then if an > x = lim sup(an) for all but finitely many an, it is...
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    How can you find a recursive sequence that converges to a desired limit point?

    Hi guys. I'm apprently stuck on the basics of the analysis. On the proof that Q lacks least upper boundary property to be precise. The example I have uses a set A (p in Q | p > 0, p^2 < 2) then q is defined as p - \frac{p^{2} - 2}{p + 2} . Then they show that if p is in A then q is in A too...
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    What is the integral over a hemisphere for a specific function?

    but where do this coefficient come from: \sqrt{a+1} Is there a general formula to expend a quartic? Or am I missing something obvious Thanks.
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    Area Inside Lemniscate Vector Calculus

    http://mathworld.wolfram.com/Lemniscate.html eq. 13 - 15
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    What is the integral over a hemisphere for a specific function?

    How did you get this expression? \frac{1+t^2}{(\sqrt{1+a}t^2+2\sqrt{a-b}t+\sqrt{1+a}) (\sqrt{1+a}t^2-2\sqrt{a-b}t+\sqrt{1+a})} when I factor {a(1-t^2)^2 + 4bt^2 + (1+t^2)^2} = (a+1)t^4 -2(a-2b-1)t^2 + (a+1) then say, u=t^2 and u1,2 = \frac{(a-2b-1)\pm 2\sqrt{(1+b)(b-1)}}{a+1}...
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    What is the integral over a hemisphere for a specific function?

    \int \frac{1}{a*cos^2(\phi) + b*sin^2(\phi) + 1} d\phi after letting t=\tan \frac{\phi}{2} I get \int \frac{1+t^2}{a(1-t^2)^2 + 4bt^2 + (1+t^2)^2} this does not look to facinating, so I let u=t^2 and this simplifies it a bit further, but introduces \sqrt{u} into denominator; I...
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    Area Inside Lemniscate Vector Calculus

    Well, you don't. What is the integral of y = ax ? ax^2 / 2, right? Can you integrate r^2 = 2a^2 (cos^2theta) then, integrate wrt to theta not a?
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    Area Inside Lemniscate Vector Calculus

    should be r^2 = 2a^2 (cos^2theta); sketch the curve to find the limits of intergration, I'd say for the right loop you integrate from -pi/4 to pi/4. Constant a controls the form of the curve. Try sketching it here http://graph.seriesmathstudy.com/
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    Area Inside Lemniscate Vector Calculus

    Hint: convert to Lemniscate equation into polar form and calculate area from there
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    What is the integral over a hemisphere for a specific function?

    Hi, I'm trying to evaluate this integral over a hemisphere: \int cos(\theta)^{a*cos^2(\phi) + b*sin^2(\phi)} dw where dw - solid angle measure,\phi is azimuthal angle and \theta is polar angle. Thus we have: \int cos(\theta)^{a*cos^2(\phi) + b*sin^2(\phi)} dw = \int \int...
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    Can someone give me an intuitive definition for differentials?

    This picture show what differential is for a function f(x) http://www.bymath.com/studyguide/ana/sec/ana4a.gif Basically, it is the change in the linear approximation for a function for a change in x, dx. dy/dx = f '(x) -> differential dy = f '(x) dx When dx is small dy is a good...
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    Exploring the Symmetry and Asymptotes of the Folium of Descartes

    Thanks for help guys! Finally got the trick of dividing one equation the other :) This yields an expression for t = 1/t0 for A)
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