Recent content by aeroplane

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    Finding point where slope of line equals curve

    You are right, there is an infinite number of solutions, solving for x gives you your answer or pi/6, and so the tangent of y=2(x-cosx) is parallel to 3x-y=5 whenever x=pi/6 +2pi*n where n is an integer. As said above, instead of considering the intersection of the two functions, you are...
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    Integration by parts can you solve this problem please

    Is it necessary to solve this using integration by parts? There's a nice substitution that makes the integral straightforward. I couldn't easily see a nice way to separate the integral.
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    Third isomorphic proof of the day.

    From what I can tell {v_{1},v_{2},...,v_{k}} is simply a finite subset of V, and {T(v_{1}),T(v_{2}),...,T(v_{k})} is the corresponding subset of images in W. As such, I don't think this question concerns bases of either V or W. That said, when a set {v_{1},v_{2},...,v_{k}} is linearly...
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    Linear independence if there is a column of zeros

    I don't think the matrix you have is a vector, vectors are either row vectors (1xm matrices) or column vectors (nx1 matrices). For this system of linear equations, each row represents a different equation. The system is then linearly independent if each row is independent, ie. row reduction...
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    What Are the Limit Points of the Set {sin(n): n a Positive Integer}?

    From http://en.wikipedia.org/wiki/Limit_point we have that x is a limit point of A={sin(n): n a positive integer} if every neighborhood of x has another element of A different from x. So if you can show that you can approximate x as closely as you wish with elements taken from A, then you have...
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    Abstract Algebra Proof question

    Definitely Deveno, but it's good to understand that it is an infinite product, otherwise you lose the uniqueness of each factorization.
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    Abstract Algebra Proof question

    Sure: we can write 108 as 108=(2^2)(3^3)(5^0)(7^0)... and 405 as 405=(2^0)(3^4)(5^1)(7^0)(11^0)... . Using our formula for (108,405)=(2^min{2,0})(3^min{3,4})(5^min{0,1})(7^min{0,0})(11^min{0,0})... we see that (108,405)=(2^0)(3^3)(5^0)(7^0)(11^0)... = 9. This divides both: 108/9 =...
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    Proving Properties of P(K) when x $\notin$ S

    Sorry, some other arbitrary set, S={s_1,s_2,...,s_n}, S'={s'_1,...,s'_n} since both are finite.
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    Proving Properties of P(K) when x $\notin$ S

    For two sets SU{x} and S'U{x} in X, SU{x}-S'U{x} is the empty set iff S=S'. Every set of X has to be at least {x}, so the difference between two elements has to be related to a difference in the subsets of S. Then you can think of X as P(S) where each element has {x} attached to it, so it must...
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    Proving Properties of P(K) when x $\notin$ S

    For 2) any element T of X is subset of K with x inside it. x isn't in S so T must be at least {x}, but it can also include elements of S since K is the union of S and {x}. If you take two elements SU{x} and S'U{x} in X, thinking about the set SU{x}-S'U{x} should help you prove the last part.
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    Abstract Algebra Proof question

    I take it (a,b) = gcd(a,b)? I'm not sure if it is just a difference in notation or not, but I think your prime factor representations should be infinite, without a index k where it stops. It's a product of all primes to different powers greater than or equal to 0, and there are an infinite...
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    Limits with sinx where x tends to infinity help.

    Solving this limit may help (you can even use l'Hopital's rule!) lim x->infinity sinx/x
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    Perpendicular distance between two equations? (parallel)

    Have you tried making a new line y_p perpendicular to both? The segment between the two y lines gives you your perpendicular distance.
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    How to Prove It, 2nd Ed. Sec. 4.4 #1b

    Looks good, I assume you worked out the transitivity property yourself, but if not you should show your work. xRy ^ yRz => |x|<= |y| and |y|<= |z|, and since <= is transitive (do you need to or have you shown this before?) |x|<=|z|, so xRz.
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    Is R with the Usual Topology Not Compact? Proving with Simple Counterexamples

    An open set like (0,n) is not compact, consider the family {C_n}={(1/n,+infinity) for n in N\{0}}. (0,n) is contained in the union, so {C_n} is a covering of (0,n). Assume it has a finite subcover. Then a finite union of C_i will cover (0,n). It's finite, so there is a largest value for i...