In the second case RegSubs treats the expression m as containing special characters. Can one tell it to treat what it receives as a literal string - perhaps some "escape" function?
 

Download regsubs_problem.mw

How to solve the following second order ODE system? (I want to solve analytically and numerically and to compare the results) Thanks. Best regards.

where

Initial conditions:

Other symbols in the equation (v_0,a_0 etc.) are constant.

MY CODE TRY:  Code.mw

I tried to write a code for matrices in the question. ( I used x instead of gamma in the code)

restart:
n:=2:
  M:= tau -> Matrix
      ( n,
        n,
        shape=identity
      )
      +Matrix
      ( n,
        n,             (i,j)->2*x*sin(i*Pi*v_0*tau)*sin(j*Pi*v_0*tau)
            ):
  C:=tau -> Matrix
              ( n,
                n,
                (i,j)->4*(i*Pi*v_0*tau)*sin(i*Pi*v_0*tau)*cos(j*Pi*v_0*tau)
              ):
  K:=tau -> n^4*Pi^2* Matrix
      ( n,
        n,
        shape=identity
      )-Matrix
      ( n,
        n,
        (i,j)-> 2*mu*(i*Pi*v_0)^2*sin(i*Pi*v_0*tau)*sin(j*Pi*v_0*tau)+2*mu*(i*Pi*a_0)*sin(i*Pi*v_0*tau)*cos(j*Pi*v_0*tau)
      ):
f:=tau -> Vector
      ( n,
        (i,j)-> x*Pi^2*(Pi/2+v_0^2*sum(((1-(-1)^k)/k^3)*sin(k*Pi*v_0*tau),k=1..infinity)-a_0*sum(((1-(-1)^k)/k^4)*cos(k*Pi*v_0*tau),k=1..infinity))*sin(i*Pi*v_0*tau)
      ):
      
 
X:= Vector(n, i-> x[i](t)): 
sys:= M(tau).diff~(X, tau$2)+C(tau).diff~(X, tau)+K(tau).X=f(tau):

how I can determined time period?

thank you

period.mw
 

Download period.mw

For some reason algsub or applyrule is not performing what they has to do.

I dont understand exactly where the below lines are wrongly declared. Clearly the variable is not substituted

Can this expression be transferred to gamma function form?

Int(exp(-Pr*(s*eta*lambda^2+lambda*eta+exp(-lambda*eta))/lambda^2), eta)

How can we solve the following pde by Maple? 

where v is velocity, v with dot is acceleration. (So, I think we will assume that acceleration is fixed.) And \delta is Dirac distribution.  E,I,m, M , g are fixed numbers.

Boundary conditions are:

Initial conditions are:

You can find the equation in the code: question.mw

Hi,

this "sum(1/(1+x)^t, t=1..infinity)" is (in my opionon) one of the most standard infinity summation and has the closed form 1/x. 
i used maple 18 and it was executed and i got the closed form 1/x.

with maple 2018 i get the non executed form, also the same inert form as "Sum(1/(1+x)^t, t=1..infinity)".

if i try "sum(1/(1+2)^t, t=1..infinity)" i get 1/2 as result.

why does the version above not working? any ideas?

thank you.

Dear friends,

I'm trying to solve a linear system of PDEs. After applying the casesplit command Maple returns: 

diff(U, z, y, x, x) = 0; diff(G, y,y,z) = diff(U,x,y,z);  diff(G,x,y,z) = diff(U,x,x,z)     

(with U(x,y,z), G(x,y,z)) 

The solution to the first equation is U = F4(x, y)+ F3(x, z) + F2(y, z) + x*F1(y, z). 

However, given this solution, I cannot satisfy diff(G,x,y,z) = diff(U,x,x,z).  What could I be doing wrong? 

Many thanks for your help.  

Hi

I have a problem with my maple. 

corrupt file 

Is there anybody who can help me solve this problem. 

Casper 

This may seem a bit trivial, but I prefer f'(x) to writing diff(f(x),x) in 1D input. How to achieve?

differential.mw

Download differential.mw

Hello,

Simple question:

Why does

restart;

(exp(I*t))^q;

`assuming`([simplify(%)], [t > 0, t < 2*Pi, q > 0, q < 1])

not simplify to exp(I*t*q)

?

The Maplecloud and maplesoft web pages only have the latest version of the physics package. 

Is there an archive of older physics packages?  ie. the latest versions to go with each of the older versions of Maple?