Hi all,

I've an implicit equation f(x,y,z)=0 resulting in a PLOT3D containing ISOSURFACE structure.

p := plots:-implicitplot3d(f,....)

As stated in docs an ISOSURFACE type of plots can't be exported.

So, question is, has anyone an idea on how to write a file containing points (xyz) from my plot p? Or any other way to export the computed points?

Thanks and regards

JiPé

Recently, I came across an addendum to a problem that appears in many calculus texts, an addendum I had never explored. It intrigued me, and I hope it will capture your attention too.

The problem is that of girding the equator of the earth with a belt, then extending by one unit (here, taken as the foot) the radius of the circle so formed. The question is by how much does the circumference of the belt increase. This problem usually appears in the section of the calculus text dealing with linear approximations by the differential. It turns out that the circumference of the enlarged band is 2*Pi ft greater than the original band.

(An alternate version of this has the circumference of the band increased by one foot, with the radius then being increased by 0.16 ft.)

The addendum to the problem then asked how high would the enlarged band be over the surface of the earth if it were lifted at one point and drawn as tight as possible around the equator. At first, I didn't know what to think. Would the height be some surprisingly large number? And how would one go about calculating this height.

It turns out that the enlarged and lifted band would be some 616.67 feet above the surface of the earth! This is significantly larger than the increase in the diameter of the original band. So, the result is a surprise, at least to me.

This is the kind of amusement that retirement affords. I heartily recommend both the amusement and the retirement. The supporting calculations can be found in the attached worksheet: Girding.mw

I will try to explain with an example, lets say i have to solve 2 equations with 2 unknowns

P := solve({3*y+x, 2*x+3+y})

I would then like to do P[1] and P[2] to get the values, but instead it gives me "x=-9/5" which make me unable to use it for things like

P[1] + P[2]

Hope you all understand, and thanks for taking your time to read my problem 

It is well known that fsolve usually increases (internally) Digits in order to obtain the desired accuracy.

But in the following example, it seems that fsolve highly exaggerates :-)   

restart;
N:=40:
Digits:=100:
F:=expand(mul(x-k,k=1..N)):
f:=evalf(F):
S:=[fsolve(f,complex)];

Error, (in fsolve) Digits cannot exceed 38654705646

Note that the bug does not appear if e.g. F:=expand(mul(x-k-I, k=1..N)):

Hi, I'd like to know if is it possible to import questions from Maple TA into Maple and use them in quizes, for example. Your help will be highly appreciated. Thank you.

i have these commands:

restart;
with(plots);
with(VectorCalculus);
with(LinearAlgebra);
f := A-B+x^y/y;

g := x^y-y;
Solve({f = 0, g = 0}, {x, y});
              / /                     y    \         \
              | | y                  x     |         |
         Solve|< x  - y = 0, A - B + -- = 0 >, {x, y}|
              | |                    y     |         |
              \ \                          /         /

but I can't get it to actually solve the equations. what do I do  ?

Hello. I have a problem with DEplot and I hope someone could help me with this:

How I can solve it for P?

P=i^(2)r+(&DifferentialD;)/(&DifferentialD; t) (1/(2)l(tetha)i^(2))+1/(2)i^(2)(&DifferentialD;l(tetha))/(&DifferentialD; theta) w

attach i(t) "corrente", l(t) "induttanza", theta "angular", w "rotary speed"graph of funtions

thanks

How to pdeplot Curl(A(x,y,z))=0 in maple

it has A1(x,y,z) , A2(x,y,z) and A3(x,y,z)

How can I produce the same output with something like alphadeg := alpharad * 180/Pi?

T := proc (p, q, R) alpharad = evalf[5](arccos((1/2)*(p^2+R^2-q^2)/(p*R))), alphadeg = 180*evalf[5](arccos((1/2)*(p^2+R^2-q^2)/(p*R)))/Pi end proc;
T(3, 4, 3.75);
           alpharad = 1.2515, alphadeg = 71.70566805

When I try alphadeg = alpharad * 180/Pi I get
Error, illegal use of an object as a name
 

Thanks! Les    AB59_20170205_Post.mw

Hi all,

I have a partial differential equation similar to the following:

The solution is that f is identically equal to 0.

However, I am having trouble solving this equation in Maple. I type the following:

pde := diff(f(x, y), x)+diff(f(x, y), y) = f(x, y)+f(x, 0);

bv1 := f(x, 10) = 0;

bv2 := f(10, y) = 0;

solution := pdsolve(pde, {bv1, bv2}, numeric, time = x, range = 0 .. 10);

When Maple tries to evaluate the last expression, I get the error

Error, (in pdsolve/numeric/process_PDEs) PDEs can only contain dependent variables with direct dependence on the independent variables of the problem, got {f(x, 0)}

It seems to have difficulties with the expression "f(x,0)". Is there some trick to typing this in a way that makes Maple interpret it correctly?

Edit: I encounter the same problem, when I try to solve the ODE f'(x) = f(x) + f(0), where f(10) = 0.

Best regards.

Hi! I have a variable polynomial expression and I want to cut off all the terms of order 3 and more, for every product of variables.

For example consider the polynomial P = x + y + a*x^2 + b*x^3 + c*x*y + d*x^2*y + e*x*y^2 + y^2, I want an operation who returns me a*x^2 + c*x*y + y^2

(terms for which the sum of exponents in x and y exceeds or less two are being deleted)

Is it possible?

Is there a way to define forms with anticommuting functions? I've tried without success:

> with(Physics):
> Setup(anticommutativeprefix={alpha,beta}):
> with(DifferentialGeometry):
> DGsetup([x, t], M):
> (alpha*dx+beta*dt) &wedge (alpha*dx+beta*dt);

                             (0 dx) ^ dt

> (f*dx+g*dt) &wedge (f*dx-g*dt);

                           -(2 f g dx) ^ dt

Thanks. Jose Carlos

hi..

how i can write this line ''for'' in maple?

thanks..

for.mw
 

Download for.mw

If binary constraints are imposed on an optimization problem and LPSolve presents a solution, is it possible to extract the variables that have zero or one assigned to them? This would be most useful if there are many variables, for example...

If a solution is returned that looks like ...

[x[001]=0, x[101]=1, x[201]=0, x[301]=1, ....], how can I filter those solutions that equal zero?

Thanks for reading!