Recent content by Mathman23

  1. M

    Homogenous diff. equation and exponential matrix

    Homework Statement Howdy, Given a matrix \left[\begin{array}{ccc}x_{11} & x_{12}\\x_{21} & x_{12}\end{array}\right] Which has the exponential matrix e^{t\cdot a} When given the eqn x'= Ax + b where b = \left[\begin{array}{c}b_1 \\ b_2\end{array}\right] I know that had it only...
  2. M

    A point of a closed convex set?

    Homework Statement Given D a a closed convex in R4 which consists of points (1,x_2,x_3,x_4) which satisfies that that 0\leq x_2,0 \leq x_3 and that x_2^2 - x_3 \leq 0 The Attempt at a Solution Then to show that either the point a: = (1,-1,0,1) or b:=(1,0,0,-1) is part of the...
  3. M

    Maple Drawing a Convex Hull in Maple

    Urgent Question: Drawing a Convex Hull in Maple Homework Statement Drawing a Convex Hull of 5 2D Points... Homework Equations None The Attempt at a Solution Hi there, I am trying draw the convex hull of the 5 points x1,x2,x3,x4,x5 below. Is this the correct way of doing...
  4. M

    How Do You Solve a Stereographic Projection Problem in Mathematics?

    Urgent Stereographic projection question... Homework Statement Given the unit sphere S^2= \{x^2 + y^2 + (z-1)^2 = 1\} Where N is the Northpole = (0.0.2) the stereographic projection \pi: S^2 \sim \{N\} \rightarrow \mathbb{R}^2 carries a point p of the sphere minus the north pole N onto the...
  5. M

    :frown: Normal curvature integral proof

    Homework Statement I need to show that the mean curvature H at p \in S given by H = \frac{1}{\pi} \cdot \int_{0}^{\pi} k_n{\theta} d \theta where k_n{\theta} is the mean curvature at p along a direction makin an angle theta with a fixed direction. Homework Equations I know...
  6. M

    Solve a very complex line integral

    Hi there, You are right :) Then I get $ \int_0^{\pi}Cos[e^{it}]ie^{it}dt and I let u=e^{it} then: du=ie^{it}dt right? so that part is already in the integral so now it's just: $ \int_0^{\pi}Cos[e^{it}]ie^{it}dt=\int_1^{-1}Cos[u]du right? I then get -2Sin[1] I...
  7. M

    Solve a very complex line integral

    Homework Statement Solve I = \int_{\gamma} f(z) dz where \gamma(t) = e^{i \cdot t} and 0 \leq t \leq \pi Homework Equations Do I use integration by substitution?? The Attempt at a Solution If I treat this as a line-integral I get: I = \int_{a}^{b} f(\gamma(t)) \cdot \gamma'(t)...
  8. M

    Solving Integrals with |a|, |b| < 1: A Hint for Fred

    Hello Hall many thanks for Your answer, By reading your very good explanation I have formulated my solution. Which goes something like this Case (1) let \gamma(t) = r \cdot e^{i \cdot t} then I_{A} = \int_{\gamma} \frac{1}{z-a} dz, where z_A =r \cdot e^{i \cdot t} +a where t...
  9. M

    Solving Integrals with |a|, |b| < 1: A Hint for Fred

    No I haven't found it in my textbook chapter yet. You mean this? http://en.wikipedia.org/wiki/Residue_theorem
  10. M

    Solving Integrals with |a|, |b| < 1: A Hint for Fred

    Homework Statement solve the integral \int_{dK(0,1)}\frac{1}{(z-a)(z-b)} dz where |a|,|b| < 1 Homework Equations Would it be relevant to use Cauchys integrals formula here? \int_{C_p} \frac{f(z)-f(z_0)}{z- z_0} dz The Attempt at a Solution If I use the above formula I...
  11. M

    How Do You Solve Complex Valued Line Integrals?

    Hi there I got a couple of question regarding the topic above Homework Statement (a) Given the integrals \int \limit_{0}^{i} \frac{dz}{(1-z)^2} \int_{i}^{2i} (cos(z)) dz \int_{0}^{i\pi} e^{z} dz (1)write this as a Line integral on the form \int_{\gamma} f(\gamma(t)) \cdot...
  12. M

    Trigometric addition of complex numbers

    thanks man it did :) Best regards Fred
  13. M

    Trigometric addition of complex numbers

    My post above regardin (2), was just an experiment, but I am unable to argue for f'(z) = f'(0) :( But anyway using post 19 again. how am suppose to get the minus between cos(z_1) * cos(z_2) - sin(z_1) * sin(z_2) = cos(z1 + z_2) Because I multiply by Eulers formula. I get...
  14. M

    Trigometric addition of complex numbers

    Hi again, I have been lookin through (2) again, and I cannot get it to work using euler. I have found in my textbook that exp(z1 + z2) = exp(z1) * exp(z2) Therefore let f(z) = sin(z) \cdot cos(z-c) where z and c belongs to \mathbb{C} Then f'(z) = cos(z) \cdot cos(z-c) -...
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