## Where is the problem?...

Hi I work with Maple 9 and I came across to this problem. I don't know where the problem is. >restart: > simplify(convert(sin(1/2*Pi*(-I*x+5)),exp)); > simplify(convert(cosh(1/2*Pi*x),exp)); does it mean that: >sin(1/2*Pi*(-I*x+5))=cosh(1/2*Pi*x); for all x's? Now look at this paradox: >x:=100; > evalf(sin(1/2*Pi*(-I*x+5))); > evalf(cosh(1/2*Pi*x)); where is the problem? cheers Sayed

## 3D Plotting Observation...

I'm working through Francis Wright's book COMPUTING WITH MAPLE. I'm not exactly sure which version of Maple this book is based on. The book's copyright is c2002. If any responders are familiar with this title or author also let me know. I'm looking on some opinions about this person. My question is that Mr Wright in one example stated that 3D plots don't admit multiple plots in [List] format. However when I typed the input: plot3d([sin(x),sin(y)], x = -Pi..Pi, y = -Pi..Pi); I still got a plot instead an error message.

## LaPlace Transforms...

Is there some sort of built in capability for doing LaPlace Transforms? or does one have to do it the "Brute Force" way ? v/r Dan

## a multibody dynamic problem(solving an 2nd order O...

several beams are connected by gemel one after another, the 1st is fixed at one end on the roof, and the last is driven by a force(fx,fy vector summation) at the end point. i am using lagrange method for the virtual displacement of angle theta[i] , and momentum balance in 2 direction (x,and y)to build the model. in the last step, i got an ODE system of 2nd order, but i cant code in maple to solve it. i think it is solveable, (6 equations, 6 unknowns). Kindly let me know how to write the code to solve it! below is the code.

> restart:
interface(warnlevel=0):
with( plots ): with( plottools ):
with( DEtools ): with( PDEtools ):
g:=9.81:
x[0][2]:=0:
y[0][2]:=0:
#initialization function of each beam,in this function, we should give 3 variables, n=the number of this #beam, la=the length of this beam, ma=the  mass of this beam
beams:=proc(n,la,ma)
global l,m,x,y:
l[n]:=la:           #length of  beam n
m[n]:=ma:           #mass of beam n
#initialize the positions of each beam
x[n][2]:=0:        #the x position of the end point of each beam
y[n][2]:=0:        #the x position of the end point of each beam
x[n][1]:=0:        #the y position of the center point of each beam
y[n][1]:=0:        #the y position of the center point of each beam
end proc;
#define the forces that applied on the end of  beam n
Force:=proc(n,fm,fn)
global fx,fy:
fx[n]:=fm:
fy[n]:=fn:
end proc:

## how to solve implicit ODE system like this?...

i have this im plicit ODE system in modeling a multibody dynamic system. theta[1](t), theta[2](t), are the angle displacement of the beams, and they are time depentent, in these 6 equations, i have the term of cos(theta[1](t)), sin(theta[2](t)),cos(theta[2](t)), sin(theta[1](t)), multipling (diff(theta[1](t),t))^2, and diff(theta[1](t),t\$2), which make them implicit equations. there are 6 unknown variables fx1,fx0,fy1,fy0(which are the forces at the end of the beams),and theta[1](t), theta[2](t). i gave the initial condition as ics:={theta[1](0) = 1/6*Pi, theta[2](0) = 1/3*Pi, D(theta[1])(0) = 0, D(theta[2])(0) = 0} Kindly let me know how to write the code to solve it! Thanks. Still below is the code: >

## Symbolic Computations under Max-Plus Algebra?...

Is there a way to do a Symbolic Computations under Max-Plus Algebra? For instance, linear algebra computations under under Max-Plus Algebra. I would like to appreciate any comments on it.

## Primitive Polynomials...

I need to search for primitive polynomials of degree n over finite fields GF(q), where q is a PRIME POWER. I have major difficulties doing that, especially when I wish to fix one of the coefficients of the polynomial. On the other hand, polynomials over GF(p) pose no problem. Does anybody have any experience in this? PLEASE HELP!

## Maple 10 update...

I noticed on the maplesoft website that there was an update available for Maple10. Is this in response to a detected product flaw ? Also is getting this update an urgent issue for a novice like myself still learning ? What I'm trying to ask is would I be missing out on some necessary feature of Maple10 by not having this update ? v/r

## Auto- and cross-correlation with Maple...

How do I perform auto- and cross-correlations in Maple?

## Sorting through multiple solutions...

My students are sometimes asked to use Maple commands that give multiple answers (solve and dsolve, most commonly) and then are asked to select a certain solution out of those returned. E.G. dsolve(diff(y(x),x) = 1/2*(6*x^3+2*sin(8*x)^2)/(y(x)^2)); returns 1 real solution and 2 complex solutions. The students are asked to select the real solution and assign it to a variable. I have making sure that Maple will select the correct solution out of the set (or list or sequence) for me by using complicated if statements. E.G. The first part of the if statement I use for the dsolve() command above is if evalf[50](subs({x=1,_C1=1},Re(rhs(solsde[1])))) =evalf[50](subs({x=1,_C1=1},rhs(solsde[1]))) then real_solution:=rhs(solsde[1]); fi; I leave off the two elif parts after the first if ... then for the sake of brevity.

## and...

how do i incorporate an and clause for my if statement? like if a=1 and b<>3 then

## how do i output text?...

i want to output text. if n=b then; n may not be completely factored end if; how do i do this?