Recent content by jahandideh

  1. J

    Solving PDE Homework Statement - Can You Help?

    thanx for suggestion my buddy. u know the orginal problem is a heat equation - one dimensional and time dependent- T_{xx}+j^{2}=T_{t} T_{t}=-1/2j\frac{b}{cL} T(1,t)=0 T(x,0)=0 j,c,b are constant and 0\leqx\leq1 i solved the problem to here: T(x,t)= j^{2} \sum...
  2. J

    Solving PDE Homework Statement - Can You Help?

    Homework Statement oh! after trying to re-solve a PDE I reached this: Homework Equations \sum\frac{4}{((2n-1)\pi)^2} (a+\frac{4(-1)^{n+1}}{(2n-1)\pi}) cos(\frac{2n-1}{2}\pi x) n goes feom 1 to \infty and "a" is a constant value. The Attempt at a Solution the solution i am...
  3. J

    What is the e^At Problem for a 4x4 Matrix?

    e^At problem! 1. Homework Statement [/b] Hi for given 4 by 4 matrix, say A, find the e^{At} which t is time variable. Homework Equations A= {\left(\begin{array}{cccc} 0 & a & 0 & 0 \\ -a& 0 & 0 & 0\\ 0 & 0 & 0 & a\\0 & 0 & -a & 0 \end{array}\right)t}Y(0). The Attempt at a...
  4. J

    How to solve second-order matrix diffrential equation?

    no! no! that was not y\dot{}=\left(\begin{array}{cc}-5 & -2 \\ 2 & -2\end{array}\right) y this is a second order system of differential equation y\ddot{}{}=\left(\begin{array}{cc}-5 & -2 \\ 2 & -2\end{array}\right)y reducing the order of the system by assuming y\dot{} = p is an idea...
  5. J

    How to solve second-order matrix diffrential equation?

    thanx yes X\dot{} = dX / dt and t is time. for first-order system of differential equations like: X\dot{}=AX+BU the solution is X(t) = e^{At} X(0)+ \int e^{A(t-\tau)} BU(\tau) d\tau for example I can solve this system : X\dot{} = {0 1 ; 2 3 } X + {0 1} u but I have problem...
  6. J

    How to solve second-order matrix diffrential equation?

    thanx yes X\dot{} = dX / dt and t is time. for first-order system of differential equations like: X\dot{}=AX+BU the solution is X(t) = e^{At} X(0)+ \int e^{A(t-\tau)} BU(\tau) d\tau for example I can solve this system : X\dot{} = {0 1 ; 2 3 } X + {0 1} u but I have problem with...
  7. J

    How to solve second-order matrix diffrential equation?

    hi all this is the general problem X\ddot{}+AX\dot{}+BX=0 let A, B,X be 2*2 matrices its application is in vibrations. any opinion will be great I can solve the first-order but ...
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