Recent content by Fellowroot

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    Infinite series as the limit of its sequence of partial sums

    Okay, now that I'm looking at it, its more than obvious. The red flag that got me was that it mentioned the word sequence and I didn't really get that because I always viewed this as a series not a sequence, as if they were different. But as you have shown me, while you are calculating the...
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    Infinite series as the limit of its sequence of partial sums

    In my book, applied analysis by john hunter it gives me a strange way of stating an infinite sum that I'm still trying to understand because in my calculus books it was never described this way. It says: We can use the definition of the convergence of a sequence to define the sum of an...
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    What is the meaning of ph(z) in complex numbers?

    I see that apparently its called phase and its related to angles, but I am missing the other details.
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    What is the meaning of ph(z) in complex numbers?

    Exactly as stated in the title. What does ph(z) mean?
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    M,N is subset of Hilbert space, show M+N is closed

    Oh yeah, apparently you use orthogonal projections.
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    M,N is subset of Hilbert space, show M+N is closed

    ^ I don't think using cauchy sequences does the job here. my teacher said I want to show closed. i don't see how cauchy shows how these spaces are closed.
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    Functional analysis, ortho basis, weakly convergent

    Thanks. I think I now have the answer to part 1 because you can use an idea from Parseval which automically shows that en weakly converges to zero. But I'm still not sure about what to do with an and un. I also think the boundedness of an plays a role. For part 2 I know that this is showing...
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    Functional analysis, ortho basis, weakly convergent

    Homework Statement This is a problem from Haim Brezis's functional analysis book. Homework EquationsThe Attempt at a Solution I'm assuming (e)n is the vectors like (e)1 = (1,0,0), (e)2=(0,1,0) and so on. We know every hilbert space has an orthonormal basis. I also need to know the...
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    M,N is subset of Hilbert space, show M+N is closed

    Homework Statement [/B] Let M, N be a subset of a Hilbert space and be two closed linear subspaces. Assume that (u,v)=0, for all u in M and v in N. Prove that M+N is closed. Homework Equations I believe that (u,v)=0 is an inner product space The Attempt at a Solution This is a problem from...
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    X' = ax+b find general solution

    I believe that I've now figured it out. I just used det(a-lamda(I))=0 solve eigen values and then get eigen vectors.
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    X' = ax+b find general solution

    Okay, so this problem was the example problem in my engineering math book. I tried to do the example before getting to the actual problems. Now I tried the same technique on the first problem and I checked out my solution to see if it worked and it only half worked. The problem I'm having is...
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    X' = ax+b find general solution

    Thank you so much! I solved the equation. x(t)=c1t+c2tln(t)+t[ln(t)]^2 the matrix solution seems to be the wronstkian of the functions next to the c1 and c2, however the third term which doesn't have a constant I'm not sure what to do with it or if it has any significant importance.
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    X' = ax+b find general solution

    Homework Statement Find general solution of the given problem in the picHomework Equations All I need to know is where they found the fundamental set of solutions. The Attempt at a Solution All I need to know is where they found the fundamental set of solutions. Please see pic. All I want...
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    Linear Algebra vector functions LI or LD

    Okay I'm still trying to master this topic. Can someone please explain to me how they got linear dependent on this following problem. u = (e^t,0) v = (0,0) w = (0, e^t) How is this dependent? I cannot for the life of me find something like au + bv = w.
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    Linear Algebra vector functions LI or LD

    actually i don't think that is so. t-t^2 is not a -2 multiple of -2t+4t^2 the 4 makes it not work like this. Also on number 5 in my homework I have this problem: u = ( 2-t,t,-2) v = (t, -1, 2 ) w = (2+t, t-2, 2 ) it says in the answer is linear dependent, yet how can this be? I do not...
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