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  1. BubblesAreUs

    Catenary problem

    Homework Statement Suppose we have a rope of length L and total mass M. Suppose we x its ends at points (xA; yA) and (xB; yB). We want to determine the shape the rope makes, hanging under the influence of gravity. The rope is motionless, with a shape parametrised by y(x) or equivalently, x(y)...
  2. BubblesAreUs

    Algebra Textbook for Abstract Algebra / Group Theory

    Excellent. I can't wait till I get my hand on this text. Thanks, once again.
  3. BubblesAreUs

    Algebra Textbook for Abstract Algebra / Group Theory

    Another question. How does the text define a ring with respect to multiplicative inverses?
  4. BubblesAreUs

    Algebra Textbook for Abstract Algebra / Group Theory

    Thanks Bill. Would you consider this textbook good as a standalone text? If so, which chapters would you recommend going through in order to learn Galois Theory. I alreadyknow that a semester course in abstract algebra is not required even though I'm planning to take it next semester.
  5. BubblesAreUs

    Algebra Textbook for Abstract Algebra / Group Theory

    I am looking for an accessible textbook in group theory. The idea here is to use it to learn basic group theory in order to take up Galois Theory. My background includes Calculus I-IV, P/Differential Equations, Discrete Mathematics including some graph theory, Linear algebra, and am currently...
  6. BubblesAreUs

    Determine whether the subset is a vector subspace

    Homework Statement Recall that F is the vector space of functions from ℝ to ℝ, with the usual operations of addition and scalar multiplication of functions. For each of the following subsets of F, write down two functions that belong to the subset, and determine whether or not the subset is a...
  7. BubblesAreUs

    Schools Low cost distance education universities

    Will be doing that once I find such a provider. It would've been great if Indian institutions offered their units to Westerners, though. They seem respectable considering that their open university grads do post-grad studies in the West.
  8. BubblesAreUs

    Schools Low cost distance education universities

    Hello all, I'm enrolled at an Australian university that offers mathematics. However, I want to fast track my education by enrolling in units over the holidays ( late Nov to early March). The problem, however, is that my institution does not offer advanced second or third year units. I'm...
  9. BubblesAreUs

    Importing survey on R Studio

    I am using R studio for a practical and I need to load a survey. It suggests that I place the following into the R template that I was provided: survey=read.csv("http://www.maths.usyd.edu.au/u/UG/IM/STAT2012/r/survey.csv") attach(survey) pulse.sf=pulse[smoke==1 & sex==2] pulse.sf Template...
  10. BubblesAreUs

    MATLAB Modelling Question

    Delta Q is a fixed variable and rather k, t depend on it as they are floating variables. MATLAB is a bit different from python in that its arrays aren't indexable. Say x = [1,2,3,4,5], I can't use x[0] = 1, x[3] = 4, etc.
  11. BubblesAreUs

    MATLAB Modelling Question

    Homework Statement Modelling the following equation: k = Delta Q / t Homework Equations Q = T2 - T1 = -40 (fixed) t = Delta Q / k. I need to find t. k can be floating so I suppose 0 to 10 minutes with 0.5 increments The Attempt at a Solution I don't have MATLAB on me at the moment...
  12. BubblesAreUs

    Set Theory? question

    k is just an integer that belongs to set Z. As for b, I think f is surjective because h is. Since f is an input of g, I'm not exactly sure how I can re-utilise my proof from part a.
  13. BubblesAreUs

    Set Theory? question

    Homework Statement Let f: X ----> Y and g: Y ----> Z be functions and let h = g o f: X ----> Z Homework Equations a. If h is surjective then g is surjective b. If h is surjective then f is surjective. The Attempt at a Solution Here h: X ----> Z a. Suppose h: x ---> z is surjective...
  14. BubblesAreUs

    LU factorisation

    Yes, for the first part, I essentially grabbed a sub-matrix and showed that its determinant is zero. To go any further than that would probably be quite tricky. Thanks Ray
  15. BubblesAreUs

    Floating point numbers

    Oh that makes sense. Now what I even more puzzling is that I'm supposed to find a min floating point such that, it plus 1 should not return 1. Interestingly, the output I am getting when adding min float and 1 is 1.
  16. BubblesAreUs

    Floating point numbers

    I just tried out sys. and got the following: >>> sys.float_info.epsilon 2.220446049250313e-16 >>> sys.float_info.min 2.2250738585072014e-308 I am looking for the smallest floating point number. Oddly, I was expecting the smallest floating point number to be greater than machin epsilon. PS...
  17. BubblesAreUs

    LU factorisation

    Yes, I get that. It seems like the rest of the stuff I did earlier is probably not required. Thanks RUber!
  18. BubblesAreUs

    Floating point numbers

    I'm finding it difficult to find the exact value of epsilon on python? Moreover, I am also supposed to find the smallest floating point number as well. Wikipedia tells me that the machine epsilon is 2−52 ≈ 2.22e-16 for 64-bit IEEE 754 - 2008? Is this the exact value on Python? Outside of...
  19. BubblesAreUs

    LU factorisation

    Homework Statement Let A = 4 -4 -1 4 -4 0 4 0 0 Use the criterion from the lectures to show that A does not have an LU factorisation such that A = LU with lower and upper triangular matrices L and U. How can you re-arrange the matrix rows...
  20. BubblesAreUs

    MATLAB question ( plot)

    Thanks Choppy. I got the script working.
  21. BubblesAreUs

    MATLAB question ( plot)

    So the array x = 0:0.01:1 is actually a loop? I can see that, but how would I nest a counter into that? Moreover, why would I have to initialise i = 0 in the beginning of the c loop? Reformed code... x = 0:0.1:1; <--- Acts as a loop from 0 to 1, 0.1 increments i = i + 1; for c = 1:1:4...
  22. BubblesAreUs

    MATLAB question ( plot)

    Homework Statement Plotting the exponential exp(-cx), 0 ≤ x ≤ 1 with c = 1, 2, 3, 4. Use a for loop. Homework Equations The Attempt at a Solution for c = 1:1:4; for x = 0:1; F = exp(-cx); end end plot(x,F) I'm not really sure where to start.. Help is appreciated.
  23. BubblesAreUs

    Comp Sci Python problem: Plotting two functions against each other

    Alrighty. Thanks for helping me out. I managed to get it running a week ago, but forgot to reply about my status.
  24. BubblesAreUs

    Comp Sci Python problem: Plotting two functions against each other

    I just noticed that by tinkering around with the function, I was able to get the velocity function to work. Unfortunately, the height function doesn't work and I've tried modifying it once again... for p in range(21): H[p] = (1/2)*g*(p**2)+(velocity0*p)+height0 return H The...
  25. BubblesAreUs

    Comp Sci Python problem: Plotting two functions against each other

    Homework Statement Enter a minimum height and velocity into plot function and return a velocity-height plot. Homework Equations The Attempt at a Solution # Find length of general list n = len(K) # Build a list for time [0,20] seconds ( Global) time = n*[0.0] # Acceleration of gravity g =...
  26. BubblesAreUs

    Depth and pressure in a submarine

    Yes that makes sense. Thus the pressure on the hull increases as the submarine dives. Correct?
  27. BubblesAreUs

    Depth and pressure in a submarine

    Homework Statement As a submarine dives, the pressure on its hull.. a. remains constant b. increases c. depends on the decrease in volume of the submarine d . decreases e. depends on the thickeness of the walls of the submarine Homework Equations P = F / A The Attempt at a Solution Not a...
  28. BubblesAreUs

    Investigating real-world situation

    Addendum: I am supposed to do some tests to collect detailed information as well.
  29. BubblesAreUs

    Investigating real-world situation

    Homework Statement Analyse the physical world around you in terms of Circular Motion/ Energy/ Momentum / Pressure/ Buoyancy/ Bernoulli's Equation. Choose one aspect you would like to investigate further. Homework Equations e.g. why some potatoes float and other do not The Attempt at a...
  30. BubblesAreUs

    C/++/# Calling C function on *nix terminal

    Thanks mate. I have managed to call out the function. :)
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