## work around for a problem in dsolve, numeric?...

Of course, there are big differences in dsolve and dsolve numeric. But also there is a difference that is subtle. It would be nice if this subtle one were not there. It may be that there is an easy work-around. Of course, the complication that is at the root of the problem may not be subtle at all. Look at the results of these two situations. First situation. > restart; > h[0]:=t->(1+t)*t^2*cos(t): > sol1:=dsolve({diff(y(t),t)=-h[0](t-1),y(0)=h[0](0)},y(t)): > h[1]:=unapply(rhs(sol1),t): > sol2:=dsolve({diff(y(t),t)=-h[1](t-1),y(1)=h[1](1)},y(t)): > h[2]:=unapply(rhs(sol2),t): > plot([[t,h[0](t),t=-1..0],[t,h[1](t),t=0..1], [t,h[2](t),t=1..2]],color=blue); Second situation

## Help on ODE from 3. to 2. to 1. order......

Hi How do i solve a 3. order ODE to a 2. order. I am using maple 10. It seems to me that i am only able to solve to 1. order via the context menu or via the dsolve command. I am a engineer student, and we often need to dsolve from 3. or 4. order down to 1. order including the ones inbetween. I hope you will be able to help me out. TIA Otto

## strange behaviour of evalhf...

Entering

Tst0:= 0.5, 27.1, 0.1, 0.2, 24.0;
tst0:= beta=Tst0[1], lambda=Tst0[2], sigma=Tst0[3], P=Tst0[4], M=Tst0[5];

someFct([1/2*P, 1/lambda*beta],[(lambda+beta)/lambda],-sigma*(1+z)^lambda);
eval(%,evalf([tst0])); subs(z=0.1, %);

myTerm:=subs(someFct=hypergeom,%);

and using evalf(myTerm) I get .9981665521 while evalhf(myTerm) gives me

Error, remember tables are not supported in evalhf

What happens here?

## Catching an error...

I'm trying to trap the exception generated when the member operator (:-) is used with a variable that is not a module. I thought the following would work:
```restart;
proc()
try
NotAModule:-mem();
catch "`NotAModule` does not evaluate to a module":
print("it worked")
catch:
print("it failed");
print(StringTools:-FormatMessage(lastexception[2..-1]));
end try
end proc();
"it failed"

"`NotAModule` does not evaluate to a module"
```
Any ideas how to fix this? The generated exception string should match the first catch statement.

## solve an ordinary differential equation with impli...

Hi, All, I am trying to solve numerically an ordernary differential equation like this diff(y(x),x) = f(y(x),ya,x) (where ya = y(x=xa), xa a known value) g(y(x=0),ya)=0 The trouble is that the initial value y(x=0) is determined by the second equation which is an implicit equation that has no analytical solution (no explicit expression), and it also depends on the solution at x=xa. Kindly let me know how to write the code to solve it! Thanks. David

## HELP SIMPLIFYING (JUST LAST 3 LINES MAINLY)...

Trying to simplify an expression and keep getting the error message "unkown operator". Same error message creeping up a lot now in my efforts to get acquainted with Maple. Getting really annoying and frustrating. Also I'm having trouble looking up specific error messages with the help feature. Is this also possible ? >

## help about Sieve of Eratosthenes...

Please, i need the code for an implementation of Eratosthenes Sieve, i need a program that calculate primes less or equal than "n", thanks and sorry for my english(i'm from Spain).

## round to a certain number of digits after the deci...

How do I round to a certain number of digits after the decimal point? Is there an easier way than the one shown below? > number:=12.3678918; > before:=trunc(number); > after:=number-before; > afterrounded:=evalf[2](after); > roundednumber:=before+afterrounded;

## format a string consisting of numbers and and anot...

How do I format a set of strings consisting of numbers and normal text strings. I want to label a color bar like it is shown below. Each last digit of a number should be below the last digit of the number in the string above. Is used the following command to create the label of the color bar: c:=textplot([seq([2.42,0.05+i/5*0.95,Join([convert(2*100*i/10,string), "*(max(energy)-min(energy))"])],i=0..5)],align={RIGHT}) P.S.: What is the maximum file size of an attachment to a post? I couldn't attach an image that's 8kb big.

## calculate the local maximum of a procedure...

How do I calculate the maximum value of a procedure within a defined region. I want to calculate the maximum value of the procedure p for Ia_IaLGmax=0..2, Ua_Ue=0..1. How can this be done in maple?

restart;
with(plots):
Ue:=75;
L:=5*10^(-6);
f:=80*10^3;
T:=1/f;
factor:=1000;
E_con:=1/2*L*(Ia_IaLGmax*Ue/(8*L)*T+1/2*Ua_Ue*Ue/L*(1-Ua_Ue)*T)^2;
E_dis:=1/2*L*((Ue-Ua_Ue*Ue)/L*(1/2/(Ua_Ue-1)*(-(Ua_Ue-1)*Ua_Ue*Ia_IaLGmax)^(1/2))*T)^2;
helpvariable:=Ua_Ue=(Ua_Ue)^2/((Ua_Ue)^2+1/4*Ia_IaLGmax);
boundary:=solve(helpvariable, Ia_IaLGmax);
p:=proc(Ia_IaLGmax,Ua_Ue)
if Ia_IaLGmax<=(-4*Ua_Ue^2+4*Ua_Ue) then factor*1/2*L*((Ue-Ua_Ue*Ue)/L*(1/2/(Ua_Ue-1)*(-(Ua_Ue-1)*Ua_Ue*Ia_IaLGmax)^(1/2))*T)^2 else factor*1/2*L*(Ia_IaLGmax*Ue/(8*L)*T+1/2*Ua_Ue*Ue/L*(1-Ua_Ue)*T)^2 end if end proc;

## Background color...

Hello! Is it possible to change the background color of worksheets or document? Regards, Franky.

## 2D, or not 2D...

I am curious as to which input mode and which document mode I should be using. I started with Maple 9.5 on Mac, when I upgraded to Maple 10 I was already accustomed to the worksheet mode so I stayed with it. I am under the impression that the document mode is more for quick calculations and producing high quality technical documents and the worksheet mode is more for programming and intensive work. Hence the names document and worksheet. If this is the wrong impression please inform me. Adding to my confusion is the choice between 2D Math input and Maple input. Up to this point I have been working almost exclusively in worksheet mode using standard Maple input. I have been working my way through the Introductory Programming Guide and I assumed this was an appropriate choice for this purpose. However, I am not sure that it is. I am now wondering if standard Maple input will eventually be phased out in favor of 2D Math input. Can someone tell me if this is the plan? Since, if it is, it would be advantageous for me to switch now. Thanks in advance.

## Help With output...

I'm going through Francis Wright's COMPUTING WITH MAPLE. c2002, and based on Maple6. can anyone explain the reason for the output that I get just for the last statement alone dealing with the change of base for logarithms ? >