Recent content by PLAGUE

  1. PLAGUE

    High School Why is the constant speed of light so unique?

    I was studying doppler shift yesterday and found out that the speed of sound wave remains the same even if the source is moving. To compensate that, the wavelength and frequency are adjusted. I know that this is also true for light which results in red and blue shift. Then why in special...
  2. PLAGUE

    Undergrad Proving Newton's forward difference interpolation formula

    Say, $$y_n (x) = a_0 + a_1(x -x_0) + a_2(x-x_1)(x - x_0) + ... +a_n(x-x_0)(x-x_1)...(x-x_{n-1})$$ Now, $$y_0(x_0) = a_0$$ $$y_1(x_1) = a_0 + a_1(x_1 - x_0)$$ or, $$a_1 = \frac{\Delta y_0}{h}$$ Here, $$h = \frac{x_i - x_0}{i}$$ Similarly, $$a_n = \frac{(\Delta)^n y_0}{h^n n!}$$ Next...
  3. PLAGUE

    Undergrad Find f(z) given f(x, y) = u(x, y) + iv(x,y)

    Can you suggest some study materials?
  4. PLAGUE

    Undergrad Find f(z) given f(x, y) = u(x, y) + iv(x,y)

    I was said that setting y equal to 0 is equivalent to setting ##z=\overline z## as done here. (see the lower half of the page) But it also doesn't make sense to me why you would set ##z = \overline z##
  5. PLAGUE

    Undergrad Find f(z) given f(x, y) = u(x, y) + iv(x,y)

    Perhaps I am missing something. I am giving the full answer here. They are taken from Schaum's Outline of Complex Variables, 2ed: Second Edition (Schaum's Outlines) by Murray SPIEGEL (Author)
  6. PLAGUE

    Undergrad Find f(z) given f(x, y) = u(x, y) + iv(x,y)

    I am given, $$u = e^{-x} (x sin y - y cos y)$$ and asked to find v such that, $$f(z) = u + iv$$. My book solves these problems and the answer is, $$v = e^{-x} (ysiny + x cos y) + c$$. I understand how it is done, using Cauchy-Riemann equations. Then, the book asks to find f(z). When doing that...
  7. PLAGUE

    Undergrad Why fixed point iteration of ##x^3 = 1-x^2## doesn't converge when ##x_0= 0##

    Or perhaps, i made mistake in my code: import math as mp def g(x): return (1-x**2)**(1/3) def pg(x): return (-2*x)*(1/3)*((1-x**2)**(-2/3)) x_0 =0.02 e = 0.0001 max_itr = 50 x_1 = g(x_0) n=0 while(n<max_itr): x_1 = g(x_0) print("{:<10} {:<10.6f} {:<10.6f} {:<10.6f}...
  8. PLAGUE

    Undergrad Why fixed point iteration of ##x^3 = 1-x^2## doesn't converge when ##x_0= 0##

    0 0.020000 0.999867 -0.013337 0.979867 1 0.999867 0.064367 -160.886288 0.935499 2 0.064367 0.998617 -0.043031 0.934250 3 0.998617 0.140340 -33.802368 0.858277 4 0.140340 0.993391 -0.094809 0.853052 5 0.993391...
  9. PLAGUE

    Undergrad Why fixed point iteration of ##x^3 = 1-x^2## doesn't converge when ##x_0= 0##

    $$x = 3/2 + (cosx)/2$$ here, if you assume $$x_0=0$$, then the derivative becomes 0. Yet, it converges!
  10. PLAGUE

    Undergrad Why fixed point iteration of ##x^3 = 1-x^2## doesn't converge when ##x_0= 0##

    I am new to numerical methods and am currently learning Fixed point iteration. I have learned that if you can express $$x = g(x)$$, and $$|g'(x_0)|<1$$, then the sequence, $$x_{n+1} = g(x_n)$$ converges to the root. I am solving $$x^3 = 1 - x^2$$ and wrote $$x = \sqrt[3]{1-x^2}$$. I took $$x_0...
  11. PLAGUE

    Undergrad Why Lagrange’s method of solving Pp + Qq=R works?

    Why along a characteristic curve dx/P = dy/Q = dz/R?
  12. PLAGUE

    Undergrad Why Lagrange’s method of solving Pp + Qq=R works?

    I am new to partial differential equations and today, I was introduced to Lagrange's method of solving PDE's. Here, is a proof that shows how Lagrange's method works. I understand the proof until it says, I mean why should, "if u(x, y, z) = c1 and v(x, y, z) = c2 are two independent solutions...