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RSS Feed for Wolfram Community showing any discussions in tag Equation Solving sorted by activeSolve System of 2nd Order Partial Differential Equations (PDEs)?
http://community.wolfram.com/groups/-/m/t/1520388
Consider the following code:
eq1 = D[C1[x, t], t] == D1 D[C1[x, t], {x, 2}];Ihtisham Khalid2018-10-18T18:04:44ZCalculate a double integral of four parameter expression?
http://community.wolfram.com/groups/-/m/t/1522428
I have tried to solve this problem using Mathcad and Mathematica, but I didn't get a solution
Fisher information matrix should be positive because diagonal values must be positive. Can you please try this for me?sumi ar2018-10-19T16:27:05ZSimulate the motion of the Earth around the Sun based on Kepler's Law?
http://community.wolfram.com/groups/-/m/t/1500089
I am using Mathematica 10.3. I want fo perform a computational analysis of the motion of the Earth around the sun based on Kepler’s laws.
Here is my code so far.
eulerStep[{t_, state_List}, h_, f_List] := {t + h,
state + h Through[f[{t, state}]]}
solveSystemEuler [{t0_state0 _}, h_, n_Integer, f_List] :=
NestList[eulerStep[#, h, f] &, {t0, state0}, n]
midptStep[{t_, state_List}, h_, f_List] := {t + h,
state + h Through[
f[{t + 1/2 h, state + 1/2 h Through[f[{t, state}]]}]]}
solveSytemMidPt[{t0_, state0_}, h_, n_Integer, f_List] :=
NestList[midptStep[#, h, f] &, {t0, state0}, n]
L = 1/2 m (x'[t]^2 + y'[t]^2) + GMm/Sqrt[x[t]^2 + y[t]^2];
D[D[L, x'[t]], t] - D[L, x[t]] == 0
D[D[L, y'[t]], t] - D[L, y[t]] == 0
xdot[{t_, {x_, vx_, y_, vy_}}] := vx
vxdot[{t_, {x_, vx_, y_, vy_}}] := -x/(x^2 + y^2)^(3/2)
ydot[{t_, {x_, vx_, y_, vy_}}] := vy
vydot[{t_, {x_, vx_, y_, vy_}}] := -y/(x^2 + y^2)^(3/2)
start = {1, 0, 0, 1};
fcns = {xdot, vxdot, ydot, vydot};
orbit = solveSystemEuler[{0, start}, 0.01, 800, fcns];
<< Statistics`DataManipulation`
xypts = Column[Column[orbit, 2], {1, 3}];
ListPlot[xypts, PlotJoined -> True];
Running the program gave the following error messages.
![enter image description here][1]
Please help me to fix my code.
[1]: http://community.wolfram.com//c/portal/getImageAttachment?filename=Capture.JPG&userId=1499975Senlau Minto2018-10-08T03:45:10ZFind what size grid could handle 4.3 x 10^17 seconds with Solve[] ?
http://community.wolfram.com/groups/-/m/t/1526408
This is my time function:
`time[x_] := Evaluate[Fit[data, {1, x, x^2}, x ]]`
How can I combine the Solve[] function with the time[] function I created to determine what size grid could handle 4.3 * 10 ^17 seconds?m I2018-10-22T01:53:22ZSolve Laplace's equation with a boundary condition?
http://community.wolfram.com/groups/-/m/t/1520613
Is there a trick to make Mathematica solve with one boundary condition?
▽^2u=0
BC : u(x,0)=0, u(x,a)=0, u(0,y)=0, y(b,y)=100ºC
Show me distribution chart to assume 0< a <100cm, 0< b <100cm in steady state.Jaeyeol Chung2018-10-18T17:22:20ZSolve the following equation with Integrate or DSolve?
http://community.wolfram.com/groups/-/m/t/1520100
Hello folks,
Think of an equation: -g+K*v=D[v]/D[t] and the conditions are when t=0, v=0; where t is time v is velocity, g is a gravitational acceleration and K is some constant. How do you input these on Mathematica so it could take the integral of the equation and gives result. I already got the result by hand as follows: v=(g*(1-e^(k*t))/K). whatever I try I cant get this result.
Thanks in advance.Najmiddin Nasyrlayev2018-10-18T14:46:37ZGet the Real part of a complex function with ComplexExpand and Re?
http://community.wolfram.com/groups/-/m/t/1511141
So I declare a complex function r[w] and I want to create another function U[w] which is defined by the real part of r[w]. So I try to use the embedded Re[] function but it returns a weird expression.
r[w]=200/(I*w*(10*I*w + 1))
If I do ComplexExpand[r[w]] I get -(2000/(1 + 100 w^2)) - (200 I)/(w (1 + 100 w^2)).
So I know that U[w] should be -(2000/(1 + 100 w^2)).
But the Re[r[w]] function returns 200 Im[1/((1 + 10 I w) w)]. Simplifying this expression by using Simplify[] and FullSimplify[] wouldn't help (even assuming that w is Real).
So how do I get the real and the imaginary part of my complex function r[w]?Daniel Voloshin2018-10-14T09:23:12ZSolve a coupled second order differential equations of two variables?
http://community.wolfram.com/groups/-/m/t/1511565
Hello friends!!
I want to solve coupled two second order and one first order differential equations of two variables
and want to plot 3D graph. My code is attached and it is giving errors.
Kindly help me to remove the errors.shivi sv2018-10-14T15:01:18ZOutput error
http://community.wolfram.com/groups/-/m/t/1511197
I am new to Mathematica and still learning the language. I have question involving a mass -spring system and need to solve a second order ODE for multiple points at multiple times but can't write it properly. Please help the question and code written is attached.![enter image description here][1]Areeb Qureshi2018-10-14T14:37:36ZPseudo-Dynamic Approach to the Numerical Solution of Nonlinear PDEs
http://community.wolfram.com/groups/-/m/t/1516751
New *THE MATHEMATICA JOURNAL* article:
----------
[Pseudo-Dynamic Approach to the Numerical Solution of Nonlinear Stationary Partial Differential Equations][1]
--------------------------------------------------------------------
*by ALEXEI BOULBITCH*
--------------------------------------------------------------------
ABSTRACT: This article presents a numerical pseudo-dynamic approach to solve a nonlinear stationary partial differential equation (PDE) *S* with bifurcations by passing from *S* to a pseudo-time-dependent PDE *T*. The equation *T* is constructed so that the desired nontrivial solution of *S* represents a fixed point of *T* . The numeric solution of *S* is then obtained as the solution of *T* at a high enough value of the pseudo-time.
- [Read full text »][2]
- [Submit an article »][3]
![enter image description here][4]
[1]: http://www.mathematica-journal.com/2018/10/pseudo-dynamic-approach-to-the-numerical-solution-of-nonlinear-stationary-partial-differential-equations/
[2]: http://www.mathematica-journal.com/2018/10/pseudo-dynamic-approach-to-the-numerical-solution-of-nonlinear-stationary-partial-differential-equations/
[3]: http://www.mathematica-journal.com/submit-article/
[4]: http://www.mathematica-journal.com/data/uploads/2018/10/Boulbitch_Output_1.gifModeration Team2018-10-16T18:22:53ZSolve system of 2nd order ODE?
http://community.wolfram.com/groups/-/m/t/1513818
New to Mathematica. Need to plot the position and velocity of 14 points. 2 are fixed 12 are in the form of a system of equations. what mistake am I making?
g = 10;
ic1 = {y[x, 0] == 0}
bc = {y[-1/2, t] == 0, y[1/2, t] == 0}
system = Table[
D[y[x, t], {t,
2}] == -100 (2*(y[x, t]) - y[x - 1/13, t] - y[x + 1/13, t]) -
10 ((2*D[y[x, t], {t, 1}]) - D[y[x - 1/13, t], {t, 1}] -
D[y[x + 1/13, t], {t, 1}]) + g, {x, -1/2 + 1/13, 1/2 - 1/13,
1/13}]
functions = Table[y[x, t], {x, -1/2, 1/2, 1/13}]
DSolve[{system, bc, ic1}, functions, t]Areeb Qureshi2018-10-15T15:29:11Z