with(Physics) :
t:=Intc(Dirac(k1+k2+k3)*phi(k1)*phi(k2)*phi(k3),k1,k2,k3) ;

# how to force
Fundiff(t,phi(-k));

# to find
3*Intc(Dirac(k2+k3-k)*phi(k2)*phi(k3),k2,k3) ;

hi friends

i have a problem in maple with an error

 restart:
 with(plots):with(linalg):
 r:=sqrt((xi-x)^2+y^2+z^2):
 sigma:=m/l:#linear mass density
 U:=Int(G*sigma/r,xi=-L/2..L/2);
 U:=normal(value(U));
 Us:=subs(G=1,m=1,L=1,z=1.5,U);
 plot3d(Us,x=-2..2,y=-2..2,axes=boxed,style=hidden,color=red,orientation=[-80,-130],numpoints=35^2,labels=['x','y','U']);

after this i see :

 Warning, unable to evaluate the function to numeric values in the region; see the plotting command's help page to ensure the calling sequence is correct.

can you help me?

Thanks for your time

Best regards

with(plots);

polarplot(1+2*sin(theta),theta=0..2*Pi);

it makes a graph made up of polar coordinate.

i wannna solve the question in cartesian coordinate

i wouldnt come up with ideas to solve it!!

please help me

for example)

y= r*sin(theta)

1+2y/r=r

y=(r^2-r)/2

...

...

y=x^n+x^n ....

x= something , something, something

Does Maple have a variable containing the directory (path) of current working file?

Thank  you.

I would like to use Newton's Method (the multivariate one) in order to solve a system of equations. From what I understand, fsolve is essentially MAPLE's version of the multivariate Newton's Method. Is there a way to do the multivariate Newton's method any other way, other than fsolve? Also, is there a way to specify our own initial guess and tolerance for the Newton's Method and to get other details such as the number of iterations?

of the improper integral of exp((1-x)/((1-x)^2+y^2)) over the unit disk x^2+y^2 <= 1 with Maple? For purists the function is assumed to be undefined at (1,0). It is not so difficult to verify that statement  by hand. It is not easy to prove that with Maple.

My try was

f := evalc(exp(Re(1/(1-x-I*y))));

VectorCalculus:-int(f, [x, y] = Circle(`<,>`(0, 0), 1), numeric);

and

evalf(Int(f, [y = -sqrt(-x^2+1) .. sqrt(-x^2+1), x = -1 .. 1]));
.

Edit. The formula for f.                  

PS.

How to find all nonisomorphic undirected graphs with 5 vertexes? Of course, with Maple.

Hello everyone,

I am working on a program in Maple and got stuck in exchanging limits for integrals. For example, if I have an expression of following type.

Eq:=4*Int(f(x), x=0..1/3)+Int(x*f(x), x=0..2/3);

I want to convert it in to an expression of form

4*Int(f(x),x=0..x)-4*Int(y,x=1/3..x)+ Int(x*f(x), x=0..x)- Int(x*f(x), x=2/3..x)

In short, I want to split both the integral at x but flip in limits in the second integral. I tried as follows which did not work

applyrule(Int(f::anything,y=c::numeric..d::numeric)=Int(f,y=c..x)-Int(f,y=c..x), Eq)

Please, help me!

Thank you for your time.

How do i proceed to solve two differential equations?

Two equations two unknowns is easy to solve in polynomial algebraic equations. Example: x+y=5; x-y=3; The solution is x=4; y=1 by adding the equations we arrive at.

The two equations are second order differential equations with two variables say temperature T (x,y) and velocity c(x,y). Assume any simple equation (one dimensional as well i.e. T(x) and c(x) which you can demonstrate with ease, I have not formulated the exact equations and boundary conditions yet for SI Engine simulation.

Thanks for comments, suggestions and answers expected eagerly.

Ramakrishnan

Dear all,

I have a question regarding the computation speed of Maple. I'm doing some numerical work with Maple and when I'm not using the build in Maple routines, but write my one routines to solve e.g. a system of partial differential equations using a finite differencing method, it takes Maple sometimes up to two hours to finish the computation. I also noticed that Maple is only using around 30% of my CPU. I know it's more efficient to do numerical work with C++ or other programming languages (at least that's what most people I know are using) but do any of you know some ways to improve the computation speed of Maple or to make it use more of my CPU to do the calculations faster?

Hey people,

I am trying to get the following code to run, but it keeps returning an error about too many arguments

restart:with(plots):with(PDEtools):
alpha_const := 0.5:gamma_const := 2.5: D1 := 0.05: D2 := 0.002:
A := diff_table(a(x,t)):B := diff_table(b(x,t)):
Selkov[1] := A[t] = 1 - A[]*B[]^(gamma_const) + D1*A[x,x]:
Selkov[2] := B[t] = alpha_const * ( A[]*B[]^(gamma_const) - B[]) + D2 * B[x,x]:

bc[1] := D[1](a)(0,t)=0: bc[2] := D[1](b)(0,t)=0: bc[3] := D[1](a)(4*Pi,t) = 0: bc[4]:=D[1](b)(4*Pi,t)=0:

ic[1] := eval(A[],t=0)=a_0:ic[2] := eval(B[],t=0)=b_0:
case1 := eval(ic,[a_0=1,b_0=1]):
case2 := eval(ic, [a_0=piecewise((x<2*Pi+1) and (x>2*Pi-1), 0.99, 1), b_0=piecewise((x<2*Pi+1) and (x>2*Pi-1), 0.99, 1)]):

Case1Default := pdsolve({Selkov[1],Selkov[2]},{bc[1],bc[2],bc[3],bc[4],case1[1],case1[2]},numerical);

Error, (in pdsolve/sys) too many arguments; some or all of the following are wrong: [{a(x, t), b(x, t)}, {a(x, 0) = 1, b(x, 0) = 1, (D[1](a))(0, t) = 0, (D[1](a))(4*Pi, t) = 0, (D[1](b))(0, t) = 0, (D[1](b))(4*Pi, t) = 0}, numerical]

My code worked just earlier today, and now it wont. If i try to run pdsolve({Selkov[1],Selkov[2]}) it says that there is an error with general case of floats. 

You help is greatly appreciated!

Hi,

I tried to use the Finance package and got:

with(Finance):
Warning, some commands in the Finance package may not work on this platform
Y := ItoProcess(1.0, mu, sigma, x, t);

Error, (in Finance:-ItoProcess) external linking: error loading external library finance.dll: The specified module could not be found.

Is it me or my pc that is causing this?

Thank you.

Murray

Hey all,

as a newbie to Maple I would likt to solve the electrical circuit, which is attached to this post. From the theory one can derive the following 6 equations:

(A)  u[smooth](t) = -(int(i[smooth](tau), tau = 0 .. t))/C[smooth]-u[smooth](0)

(B) u[smooth](t) = R[komp]*i[komp]

(C) u[ckomp](t) = (int(i[load](tau), tau = 0 .. t))/C[komp]-(-u[ckomp](0))

(D) u[loadt](t) = R[load]*i[load]

(E) u[smooth](t) = u[ckomp](t)-u[load](t)

(F) i[komp](t) = i[smooth](t)-i[load](t)

My aim is tio get either the voltage u[load](t) or the current i[load](t). Beside all parameter values I know the inital voltages at the capacities, called u[smooth](t=0) and u[ckomp](t=0). Both values are not zero in general!!!!

Do you have any idea how I can solve this with Maple? First I habe tried to solve this with "solve()" but get a solution with "solve()", I need to derive the equations to get rid of the integrals. But through the derivation my initial condictions vanish, too.
I have attached my Maple worrksheet as well: igl.mwigl.mw

BR

 Sebastian

P.S.: Here is the circuit:

There are quite a few useful resources, like TAs and documents in the startup page, however, I can only access them by clicking the links. Where are those files located on the disk? (Mac OSX)

Hi

I want to plot this equation to obtain 5 curves, then the maximum point  of eath curves link together.

But I can not plot this equation;anybody can help me?

restart; Eq := x-(r+3.1*10^7*exp(-11616/(1.98*T)))/(3.1*10^7*exp(-11616/(1.98*T))+1.8*10^18*exp(-29691/(1.98*T))) = 0; R := [0, 0.1e-2, 0.1e-1, .1, 1.6]; plots[implicitplot]([seq(eval(Eq, r = R[i]), i = 1 .. nops(R))], T = 0 .. 500, x = 0 .. 2, color = [red, blue, green, yellow, black], gridrefine = 5)