Hello!
I try to solve the eq1, eq2, eq3, and eq4.
I simplified the 4 equations to rs1 and rs2
to get the solution t3 and t5.
Then, I check the solution by subsituting Eq(14)
into Eq(10). The result is right. The rs1 equation
was found by numerical tests.
However, it is not correct for the eq1, eq2, eq3,
or eq4. I do not understand why it is not correct.
Please tell me the reason and how I can solve and obtain
correct solution. The worksheet can be found in the

File Manager
Thank you for your time and help.

October 25 2006
PyWiz 8
Hi
Please see Spiderflygrid2.mws
A spider is on the floor of a cubical room of side 1. Its position is given. Where must the fly position itself to be as far as possible from the spider?
My attempt minimizes the square of the twelve possible distances. This is m.
m:=min(seq(cd[i], i=1..12));
Partial derivatives of m are found with respect to xf (the x coord of the fly)
eq1:=diff(m,xf);
... & with respect to yf (the y coord of the fly)
eq2:=diff(m,yf);
These two equations are then solved simultaneously.
solve({eq1,eq2});
Maple gives an error message - is this due to the discontinuities in the expression m? Or (more likely) a fault in my Maple code?

Hello,
I am quite new to Maple and I am trying to solve a system of 3 non-linear equations in 3 variables (A,zp,zh). I have tried the solve command, but after waiting few hours I have decided to stop the computation. Could someone help me with this?
The system is as follows
eq1 := 1/(-138.8888889/(24000000-50/3*zh)^1.5-.50/zh^1.5-122.7222223/(-8640000+47/3*zh)^1.5)*(5.465600000*A/(1+zp)^.5e-1
+(-16.66666667/(24000000-50/3*zh)^.5+1.0/zh^.5+15.66666667/(-8640000+47/3*zh)^.5)*(.3e-1+.3*A))=0;
eq2 := .4879000781e-6/A*(1+zp)^2.05*((-1952000.00*A/(1+zp)^1.05+50/3)*(.3e-1+.3*A)-10.93120000*A/(1+zp)^.5e-1

Hi,
I'm trying to get maple to output the numerical answer, from a call to dsolve, to an external txt file; but I'm having a bit of trouble. I want to do this so that I may then plot the results in an external program like easy-plot, or just analyse them.
I'm using a "read" command in Maple to read in a procedure from a txt file (shown below), which I then execute in Maple:
#Utilise prime notation for derivatives wrt t:
with(PDEtools, declare):
with(plots):
declare(y(t), prime=t, quiet):
#Also shorten output notation:
alias(y=y(t),y0=y(0),yp0=D(y)(0)):
#define the ODE:
ODE:=diff(y,[t$2])-(1-y^2)*diff(y,t)+y=0;

October 17 2006
bjain 8
Download 569_ODE-25 Reactions.doc
Hi,
I want to solve 25 set of differential equation for unknown variable and contants.
Problem Statement: Solve the following set of differential equations for concentrations terms in terms of CA0 and t
CA, CB, CC, CD, CE, CF, CG, CH, CI, CJ, CK, CL, CM, CN, CP are the variables and k1 to k25 and CAO are constants
Initial Values: t=0 CA=CA0 and CB=CC=CD=CE=CF=CG=CH=CI=CJ=CK=CL=CM=CN=CP =0
How do I proceed for the same?
Regards,
Bikash

Hi,
I am trying to use fsolve to find the roots of p non-linear equations. These vary from 2 dimensional to, so far, 5 dimensional.
I'm really trying to minimize the log likelihood of an ARCH time series:
L := (t) -> 1/2*T*log(2*Pi)+1/2*Sum(log(h(t)),t = p .. T)+1/2*Sum(y[t]^2/h(t),t = p .. T):
where
h := (t) -> alpha[1] + alpha[2]*y[t-1]^2 + alpha[3]*y[t-2]^2 ... + alpha[p]*u[y-p]^2:
and
y[t] are observed data.
I've used the p partial derivatives to solve for dL/dalpha=0 using fsolve and intervals alpha=0..1. Occasionally, it works fine and estimates the parameter vector alpha reasonably. However, sometimes it takes about 30-60 seconds and just returns the equation and no answer:

October 10 2006
Rick 28
Hi,
I have a question about Gröbner bases and using the Rosenfeld_Grobner algorithm in diffalg. What is best to use? If the equations only contain time differentiated variables, is it better to differentiate the equations "by hand" first and let the Gröbner package deal with the problem or is it better to just plug the whole thing into diffalg from the start?

Given N-1 independent (not necessarily linear) equations in N variables, how do I tell Maple to find solutions in terms of a specific variable?
For example:
with(RealDomain);
eq1:=x-1=a*cos(theta);
eq2:=x+1=a*sin(theta);
I want to find a and theta in terms of x:
a=sqrt(2*x^2+2), theta=arctan((x+1)/(x-1))
solve({eq1,eq2},[a,theta]) appears to give me solutions based on elimination of x.

Dear All,
I'm working on a problem in differential equations where I need to compute the n-th power of a differential expression. Can Maple be taught to differentiate polynomial functions without carrying out the multiplications / simplifications that it usually does? For example:
diff(-2*c/x^3,x); gives the answer 6*c/x^4.
I want it to return: (-3)(-2)*c/x^4.
Ideally, I also do not want it to simplify sums of such results.
Thank you very much, I appreciate your help!
Andrea Bruder

Hi there!
I have a system of four non-linear equation that I can solve with fsolve after having provided the parameter values. I wrote a procedure which passes the parameters values, define all the equations and call for fsolve which provides the solution value for all the four unknowns.
Now, I would like to plot each solution against the input parameters passed to the procedure. In other words, I want to make some comparative statics which shows as the solution changes as the parameters change. Of course, I'll make only two parameters varying simultaneously.
I tried plot3d, but it doesn't work, because the procedure is not really a function I guess.

The attached file solves a system of equations in a couple of seconds in maple 9.5
But in classic worksheet maple 10.04 after many minutes it gobbles up gigabytes of memory and then ends with an error.
The file belows shows the details but it has the form
sys:={eq1,...eq22}:
solution:=solve(sys,{var1,...var22}):
Any comments very much appreciated.
Download 2129_No Solve.mws

Hi.

I am trying to debug a small piece of code I've written.

I have a procedure for solving some quite complex equations. For single points in space.

I have a procedure that:

has some quantities passed to it,

brings in a 2 by 80

Does a for loop for each of the rows in the data, to take the first col value, and puts that along with the vars passed to it into the first procedure. It then works out the difference between the value given by the first procedure and the second col. Squares this and adds it to the total.

I'd like to use the NPLSolve minimize function to minimise this total squared sum of differences, by passing differnt values to the second function.

September 04 2006
yvette 8
Hi
I'm new to Maple. I've had it for years and am just now getting into it. My problem is how to simultaneously solve a set of equations that feature some nonlinear terms. This isn't a set ODE's. They are algebraic equations with nonlinear integral terms like, I2:=int(cos(Pi/2/Theta*e)^4.545*sin(e)*cos(e-phi),e=theta..Theta); There are 3 variables to solve for after the variable theta has been specified. Equation 1 has the nonlinear terms and the other 2 equations are linear. I can post all 3 equations if someone can help.
I saw an example on this site for a vibration problem solved with the Runge-Kutta method but the dsolve command was used and mine aren't ODE's. I have version 7.

August 31 2006
Mak07 8
I am solving a set of equations with 4 variables. The solve comes out as an unordered set each time and I cannot figure out how to sort them. Btw, I am using Maple V Release 4 (yes it is old. :-))

So here is the results of the solve

sols := {b1 = 84.92147612, b4 = 87.31363038, b2 = 101.6273403, b3 = 86.10094107}

What i need to get is either the solution ordered {b1,b2,b3,b4} or the indices of the variables in order. I have tried the following:

Isort:=proc(L) local a,i;

> a:=sort([$1..nops(L)],evalb((i,j)->L[i]<=L[j])); [seq(L[i],i=a)],a end:

as recommended from another post and i get the following error: