nm

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12 years, 190 days

MaplePrimes Activity


These are replies submitted by nm

@Alejandro Jakubi 

" Integration is an area where bugs are  being reported quite frequently, but has not been improved for many versions (years) already."

Why would that be? There are so many PhD math people out of work looking for a job. Can't Maple hire one or two or three of them and have them fix all these math bugs? very strange.

@gkokovidis 

You do not need to explicitly declare Array, etc..  you can do it on the fly?

restart:with(plots):
eq1:=0.199563349672261+0.01*x^1.13-0.018*x^1.13;
eq2:=.29-0.01*x^1.003-0.013*x^0.97966;
A1:=plot(eq1,x=0..10,color=green):
A2:=plot(eq2,x=0..10,color=blue):
display(Vector[row]([A1,A2]));


@Axel Vogt 

Thanks Axel, it displayed US. But I followed  Markiyan Hirnyk instructions and found the thing to click on at the bottom of the web page, and now it is in English. I agree with you, this is normally put at the TOP of the web page in clear place, not hidden at the bottom of the page to change the language.ANd I still have no idea why it switched to French on me. But now I know what to do it this happens again :)

 

@JohnS 

sorry, not following you, so not able to know what to do, But I am sure someone who knows this better than me will be able to help. good luck.

@Carl Love 

Great. thanks. So may be this is a skill that needs to be acquired to know which command to use and which not to use each time, and it is not something one can reason about using logical steps.

For example, why would

convert(s,trig);
combine(%):

work, but not

convert(s,trig);
simplify(%);

and not

convert(s,trig);
convert(%,sinh);

and not

convert(s,trig);
convert(%,trigh);

and why simplify was needed to tell Maple that is same as

I mean, if this processes is based on trial and error method, then that is not a good way to go about it, but if there is a logic behind it, then that will be better.

computing the indefinite integral, then evaluating it on the intervals, then letting {p=1,n=1,q=1,m=1} in the result gives a divide by zero. Not -(1/2 I)/Pi. Just an observation, that is all.

restart;
assume(m::integer, n::integer, p::integer, q::integer,x::real):
h:=(x,m,n,p,q)->-(1/8*I)*(exp((2*I)*Pi*x)-1)^2*(exp(-(2*I)*Pi*x*(n-q+2))-exp(-(2*I)*Pi*x*(n-q+1)))/(Pi^3*x*(m-x)*(p-x)):
sol:=int(h(x, m, n, p, q), x):
sol:=subs(x=infinity,sol)-subs(x=-infinity,sol):
subs({p=1,n=1,q=1,m=1},sol);

     Error, numeric exception: division by zero

 

@acer 

strange that the good and bad ODE both give same analytic solution.

 

@Andriy 

"You should not use any CAS for such type of tasks."

I think the above statment is not fair and assumes many thing about the user.

Many use a CAS to verify a calculation that was already done by hand. For me, that is the main use of a CAS. To help me find if I made an error or not.

It is also possible that this specific calculation could be small part of very large program. So asking someone not do this step using CAS is simply not possible in this senario.

@Carl Love 

 

screen shot.... thanks

@Carl Love 

thanks. That is actually what I tried. it puts the 1/2 below the whole expression, which is not what I want. I wanted it to show like you showed it. I am using Maple 17.02 on windows 7, 64 bit. I use worksheet. Here it is:

@acer 

thanks. The syntax you showed really helps and I will use them.
But as I said, I do not have specific problem. Just was looking for shorter syntax. A typical use, is when I solve a set of ODE's and want to multiply the solution by some A matrix. So now, I was doing this:

ode1:=2*diff(x(t),t)+x(t)+diff(y(t),t)+2*y(t)=exp(t):
ode2:=3*diff(x(t),t)-7*x(t)+3*diff(y(t),t)+y(t)=0:
sol:=dsolve({ode1,ode2},{x(t),y(t)}):
A:=<< -10/3|-5/3>,<17/3|4/3>>;
A.convert(convert(map(rhs,sol),list),Vector);

with your syntax, I can do the last line above like this:

    A.<map(rhs,sol)[]>;

which is much shorter.   (I tend to prefer shorter syntax :)


thanks

@Carl Love 

Actually, I just tried it and it worked. No special reason. But simplify() works at that stage, so will edit my answer and replace convert to simplify.

 

I assumed you had a type  in (x+y)^2+(1)/x+y  and you meant  (x+y)^2+  1/(x+y), else the result you want to obtain do not follow....you might want to fix your question

@Carl Love 

Maple prime will not let me edit my own answer, it says "You do not have permission to delete this document". So, I'll see if it works here:

plot([f(x),diff(f(x),x)],x=-3..3,discont=true,legend=[typeset("f(x)"),typeset("f'(x)")]);


 

@Carl Love 

Thanks. I searched/googled for clear variable in Maple and did not see this. But this works.

In Particular, I got wrong information from this site:

http://www.cs.princeton.edu/courses/archive/fall09/cos323/symbolic/mapleSym.html

"This was done to clear the variable. Maple, unlike Mathematica, does not
have a Clear function for variables. Before using a variable in an equation
be sure you know what it represents or if you are not sure assign a constant
such as 1 or 0 to it."

 

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