pasmith's latest activity
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Ppasmith replied to the thread Great circle between two points on the Earth's surface.I would rotate the sphere so that one point is at the north pole (0,0,1). Then ##\theta## is just the colatitude of the image of the...
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Ppasmith replied to the thread Undergrad Question about using Newton's Method to solve a system of equations.If ##A## is invertible, then solving ##Ax = b## by Gaussian elimination where ##b## consists of zeros except for a 1 in the ##i##th row...
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Ppasmith replied to the thread Undergrad Question about using Newton's Method to solve a system of equations.We don't solve linear systems numerically by finding an inverse matrix; that is incredibly inefficient. Instead we use other methods...
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Ppasmith replied to the thread Investigating the real roots of a cubic equation.Your working appears to be correct, and I obtained the same result by considering the discriminant of ##f##. What did you do to verify...
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Ppasmith replied to the thread Undergrad Do non-orthogonal coordinate systems mean dependent coordinates?.Coordinates are independent, whether orthogonal or nonorthogonal. Introducing such a dependency restricts you to a curve or a surface...
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Ppasmith replied to the thread Undergrad Limit behaviour of Fibonacci sequence.Alternatively, we can also consider that the general solution of ##F_{n+2} = F_{n+1} + F_n## is $$\begin{split} F_n &= A \left( \frac{1...
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Ppasmith replied to the thread Undergrad Limit behaviour of Fibonacci sequence.A slight correction is indeed required. From ##a_n \geq 1## we have ##a_n \varphi \geq \varphi ## so that $$ |a_{n+1} - \varphi| \leq...
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Ppasmith replied to the thread Undergrad Limit behaviour of Fibonacci sequence.There is a much easier way to arrive at these results. From ##a_{n+1} = 1 + a_n^{-1}## and the definition of ##\varphi## we can obtain...
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Ppasmith replied to the thread Undergrad Why should we need to re-prove theorems that have been proved already?.So that we understand the proofs, and can satisfy ourselves that they are indeed correct proofs. We don't take other people's word for...
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Ppasmith replied to the thread Undergrad Why are these cycles disjoint and of equal length?.It is a fact of basic group theory that conjugation preserves the order of an element (because conjugation is an isomorphism from a...
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Ppasmith replied to the thread Undergrad A counterexample to "the integral of the limit is the limit of the integral".A generalization is to fix ##g: [0,1] \to \mathbb{R}## and let $$f_n : [0,1] \to \mathbb{R} : x \mapsto \begin{cases} ng(nx) & x < \frac...
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Ppasmith posted the thread Undergrad A counterexample to "the integral of the limit is the limit of the integral" in Calculus.I was going to append this to @chwala's thread here, but thought it deserved a new thread. For ##n \geq 1##, define $$f_n : [0,1] \to...
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Ppasmith replied to the thread Undergrad Uniform convergence and pointwise convergence.Consider also ##e^{-n\sin \theta}## for ##\theta \in [0, \pi]##.
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Ppasmith replied to the thread Modeling a graph that shows age in relation to depth of an ice sample.Responses, like the original post, should be typed and make use of LaTeX rather than screenshots.
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Ppasmith replied to the thread France to ditch Windows for Linux.I was working at the UK's Ministry of Defence just over 10 years ago when they rolled out Office 365. This involved the MOD making...