Recent content by s_j_sawyer

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    Velocity of boat in river with varying current

    Nevermind I got it. I was overthinking it apparently...
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    Velocity of boat in river with varying current

    Well \sigma is the steering angle... my professor told us just to assume the boat had a constant speed, which is why I introduced the formula V_x^2 + V_y^2 = 1^2 and in thus doing so assumed the speed to simply be 1. Can someone read the question and see if I'm interpreting...
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    Velocity of boat in river with varying current

    Homework Statement See attached. Homework Equations The Attempt at a Solution I originally began by assuming the rate was constant, obtaining the equations V_x^2 + V_y^2 = 1 \tan{\sigma} = \frac{V_y}{V_x} with the assumptions V_x(\sigma) = f(\sigma) V_y(\sigma) =...
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    Are These Regions in R^2 Compact?

    Homework Statement Determine whether the following in R^2 are compact or not. (i) [0,1] X [0,1) (ii) [a,b] X [c,d] where a < b, c < d The Attempt at a Solution I have seen this notation before but I never knew what it meant.
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    Do Fourier Coefficients Decay with Increasing n?

    Ok I followed everything you said but I still don't see how this relates to what I'm trying to show. The fact that there is a /n necessary is really confusing me. i.e. |an| <= K/n and not just KEdit: Ok I may have gotten it. I think the solution is |an| <= |a1|/n and |bn| <= |b1|/n There's...
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    Do Fourier Coefficients Decay with Increasing n?

    Homework Statement Let f be a C1 function on [-pi,pi]. Prove the Fourier coefficients of f satisfy |an| <= K/n and |bn| <= L/n n=1,2,... Homework Equations an = 1/pi * int[-pi..pi] (f(x)*cos(nx)) dx bn = 1/pi * int[-pi..pi] (f(x)*sin(nx)) dx Sorry if my form is slightly...
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    How Do You Solve a System of Linear ODEs with Equal Second Derivatives?

    Homework Statement Solve this system of linear ODEs: 1) x''(t) = x + y 2) y''(t) = x + y Just fyi, this is part of a much larger problem but I need to solve this system! Homework Equations See above. The Attempt at a Solution Okay so I think the most logical way to solve...
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    Prove ||w + z|| <= ||w|| + ||z|| for complex vectors

    Sorry to double post but I didn't think simply editing would bump this up. Alright so I played around with this some more but still could not get it to work. I tried to prove this using the method of squaring both sides for the regular 'scalar triangle inequality' proof like so: ||w +...
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    Prove ||w + z|| <= ||w|| + ||z|| for complex vectors

    Oooohhh deeaarr how embarrassing. Thank you for that insightful information. I should be able to get it now.
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    Prove ||w + z|| <= ||w|| + ||z|| for complex vectors

    Homework Statement Let z, w be complex vectors of C^n. Prove ||w + z|| <= ||w|| + ||z|| (using the standard inner product for C^n) (i.e. <w,z> = w*z', where * is the dot product and ' denotes the complex conjugate) The Attempt at a Solution Well, I found that ||w + z|| =...
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    Show that this orthogonal diagonalization is a singular value decomposition.

    Well, A has an orthonormal set of n eigenvectors, which would therefore be the same as A^T, but I don't know how to use this in the proof.
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    Show that this orthogonal diagonalization is a singular value decomposition.

    Homework Statement Prove that if A is an nxn positive definite symmetric matrix, then an orthogonal diagonalization A = PDP' is a singular value decomposition. (where P' = transpose(P))2. The attempt at a solution. I really don't know how to start this problem off. I know that the singular...
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    Singular Value Decomposition of an nxn matrix?

    I was just wondering if it was possible to find the singular value decomposition of an nxn matrix such as 1 1 -1 1 I tried this but then when finding the eigenvectors of A^T*A I found there were none (non-trivial anyhow). So, is this not possible? EDIT: How embarrassing I made an...
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    Trig Identity Question Sort of

    Homework Statement Okay so the objective here is to express y(t) = cos(t - b) - cos(t) in the form y(t) = Asin(t - c) where A and c are in terms of b.Homework Equations For easy reference, here is a table of identities: http://www.sosmath.com/trig/Trig5/trig5/trig5.html The Attempt at a...
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    Prove A is symmetric iff x*Ay = Ax*y

    So you're saying x*Ay = x*By does not imply A = B? Also, I've proven that any square matrix can be written as a sum of a symmetric matrix and a skew symmetric matrix (i.e. A = B + C, where A is nxn and B is symmetric, C is skew symmetric) but I can't seem to prove C = 0 using my original...
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