i found this program in mapleprimes 

hi, i have a procedure to multiply two matrices below

mymatrix:=proc(A::Matrix,B::Matrix)

local i,j,k,q,C;

uses LinearAlgebra;

C:=Matrix(RowDimension(A),ColumnDimension(B));

for i from 1 to RowDimension(A) do

for j from 1 to ColumnDimension(B) do

C[i,j]:=0;

for q from 1 to ColumnDimension(A) do

i have a systems of differential equation:

J[n]=2*A[n]

S[n+1]=J[n]

A[n+1]=S[n] + 0.5*A[n]

with initial condition A[0]=10, J[0]=30, S[0]=5

i have a had time writing a procedure for this systems. help please

do i need a for command for this procedure

how do you analytically and numerically solve the IVP: y" + 4y' + 13y = cos2t, y(0)=2, y'(0)=-1.