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1h
revised How to define an exclusion zone for NDSolve
edited tags
8h
reviewed Leave Open Attempting to modify parts of a multi-level association in-place
8h
comment How to manipulate the initial conditions in a ODE system?
You can format inline code and code blocks by selecting the code and clicking the {} button above the edit window. The edit window help button ? is also useful for learning how to format your questions and answers. You may also find this this meta Q&A helpful
8h
reviewed No Action Needed How to manipulate the initial conditions in a ODE system?
11h
reviewed Close How to symbolically integrate 2D exponential function?
13h
reviewed Reviewed How to properly plot a unit pulse?
13h
comment How to properly plot a unit pulse?
Welcome to Mathematica.SE! I suggest the following: 1) As you receive help, try to give it too, by answering questions in your area of expertise. 2) Take the tour! 3) When you see good questions and answers, vote them up by clicking the gray triangles, because the credibility of the system is based on the reputation gained by users sharing their knowledge. Also, please remember to accept the answer, if any, that solves your problem, by clicking the checkmark sign!
13h
comment Using Solve with Mod
It seems to me Solve is working exactly as it is supposed to. The C[1] is a parameter, that parametrizes the infinitely many solutions of the equation. You can set it to any nonnegative integer with a replacement like this sol /. C[1] -> 0.
13h
comment Using Solve with Mod
Brute force: Sort@DeleteDuplicates@Table[Mod[3^x, 71], {x, 70}]
13h
comment Using Solve with Mod
The {} returned by Solve indicates there are no x that solve the equation.
14h
comment How to define an exclusion zone for NDSolve
@bel The tag numerical-integration explicitly includes questions about NDSolve.
15h
comment How to define an exclusion zone for NDSolve
Oops, just noticed V7 -- that was too long ago....You should probably mention that in the body of the question (assuming that's what the tag means). For newer versions, the comment would be: I'm unaware of any option named StoppingTest. Look up WhenEvent, paying particular attention to the action "StopIntegration".
15h
comment Using NDSolve to find particle trajectory
@drN It's a bit of a mystery, isn't it, since the LHS of the pos''[t] evaluates to 3x3 matrix and the RHS is a 3-vector. But it works, I guess: Look at the diagonal of the matrix in Inactivate[{e + Cross[pos'[t], b] == m/q pos''[t], pos[0] == {0, 0, 0}, pos'[0] == {0, 0, 0}}, Equal] /. sol /. t -> 1. It probably minimizes the norm of the residual (the matrix minus the vector), which in this case would lead to the correct solution, but if so, you'd think the large norm would cause an error/warning.
15h
answered Using NDSolve to find particle trajectory
16h
revised Using NDSolve to find particle trajectory
edited tags
16h
answered Brackets around each item in matrix
19h
reviewed Leave Open Plotting function with unique symbols
19h
comment Plotting function with unique symbols
@Mr.Wizard It seems to me the underlying problem is that Evaluate should be placed outside the list, Evaluate@{X[[1]], 0, 1}. This is the issue in many posts, such as (5235) and (47907), and is also explained in this answer. I couldn't find one in which the issue was specifically using Evaluate in the second argument to Plot. It's usually the first argument.
19h
comment ContourIntegral keyword
Somewhat related Q&A: (17429), (39987), (74089)
19h
revised ContourIntegral keyword
added 152 characters in body