## How to correct this error...

I don't know how overcoming this error . Thank you. MyPackage := module() export f1, f2; local loc1; option package; f1 := proc() loc1 end proc; f2 := proc( v ) loc1 := v end proc; loc1 := 2; end module: savelib('MyPackage'); Error, cannot open archive, C:\Program Files\Maple 2018\lib, for writing. restart; with(MyPackage); Error, invalid input: with expects its 1st argument, pname, to be of type {`module`, package}, but received MyPackage

## How to build a library containing my own procedure...

How to build a library (package) containing my own procedures ? Could you give me an example. Thank you.

## EDIT: within "if": f(1,1)<3.0 condition cannot be ...

Hello,

I want to create a plot of a gradient field of a function with singularities I want to draw arrows only where the function has values below 3,   or written: where f(x,y) < 3.

MY CODE:

potfeld := f(x, y) -> 1/sqrt(y^2+x^2);
for i to 5 do
for j to 3 do
if sqrt(i^2+j^2) <> 0 and sqrt((i-2)^2+j^2) <> 0 and potfeld(i, j) < 3
then P[i, j] := arrow(`<,>`(i, j), `<,>`((D[1](potfeld))(i, j), (D[2](potfeld))(i, j)))
else P[i, j] := arrow(`<,>`(i, j), `<,>`(.1, .1))
end if
end do
end do;
Pseq := seq(seq([P[k, l]], k = 1 .. 5), l = 1 .. 3);
display(Pseq, view = [1 .. 5, 1 .. 3], scaling = constrained);

RESULTS IN:
Error, cannot determine if this expression is true or false:  (1/2)*2^(1/2) < 3.0

The "(1/2)*2^(1/2)" are the value of the function potfeld(x,y) evaluated at (1,1).

I ask for your help, as with many changes and variations I have not managed to solve this issue.
+Thx and regards+

## How to show 2 expressions are equivalent ?...

A line is deternined on one side by 16*x-2*y-11*z=0, 14*x-y-10*z=3 and on the other by (x-2)/3=(y-5)/2=(z-2)/4. Are they equivalent  ?  Thank you.

## Error in Maple code...

I have made a procedure named Eratosthenes that will return a sequence of all the primes less than some given number N which must be a positive integer. However, I couldn't figure out the error but still, the code is not working either. Can anyone please go through my code to let me know if I have a mistake? Thanks.

 >

## Couldn't solve the following using Maple....

I have been trying to solve the following question using Maple for quite some time but couldn't do it. Any guide will be highly appreciated.

P.S: I have just started learning it by myself in the last few days. I have been following An Introduction to Modern Mathematical Computing: With Maple. If you could suggest a more useful text, that would be helpful.

## Maple command "Matlab()" does not work for me...

Hi,

I'm trying to use "Matlab()" command to convert Maple expression into Matlab's expression.

but for some reason it doesn't work.

it works for simple expressions but not this one. It is just a long expression with only some symbols, and the most basic math operations. I don't see why it fails.

It says: "Error, (in Translate) options... not recognized"

I'm attaching the maple code so you can see the error.

The reason I'm using it is because Matlab could not solve the equation in the file (even numerically). So I wrote the same equation symbolically in Maple so I can copy the symbolic solutions to matlab and use them instead of matlab's 'solve' command.

Hope anyone can help with it.

Here's the code attached:

calc_theta.mw

## How do I assign a letter to the lhs of each elemen...

Good day all.

If I generate a list containing (say) 100 elements or more, and each element is an ordered pair - is it possible to assign a letter to each element? The first 26 elements will have equal A to Z, the next 26 will take A1 to Z1, and so on.

For example if the list is [ [5,3], [2,5], ..., [3,1]], how do I construct it to become [A=[5,3], B=[2,5], ..., V3=[3,1]]?

Thank's a lot for your time.

MaplePrimes_Label_Lists.mw

## how to draw these 3 lines and then project them on...

how to draw these 3 lines and then project them on the plans Oxy,Oxz,Oyz;
3 given lines a := [3*t-7, -2*t+4, 3*t+4]; b := [m+1, 2*m-9, -m-12];c:={x = -200/29-2*t, y = 114/29+3*t, z = 119/29+4*t}, how to show these lines and the projections on the 3 planes ? Thank you.

## How to show that these 2 procedures are correct or...

A := [1, -2, 3]:u := `<,>`(0, -2, 2):v := `<,>`(5, 8, -3):
PL := proc (A, u, v) local d, Det, AP, t, U, V;
AP := `<,>`(x-A[1], y-A[2], z-A[3]);
Matrix(`<|>`(`<,>`(AP), `<,>`(u), `<,>`(v)));
Det := LinearAlgebra:-Determinant(%); d := igcd(coeff(Det, x), coeff(Det, y), coeff(Det, z), tcoeff(Det));
print(`Une équation cartésienne du plan est :`);
t := Det/d; print([t = 0]);
print('Une*représentation*paramétrique*du*plan*est; -1');
U := convert(u, list); V := convert(v, list);
[x = lambda*U[1]+mu*V[1]+A[1], y = lambda*U[2]+mu*V[2]+A[2], z = lambda*U[3]+mu*V[3]+A[3]] end proc;
PL(A, u, v);

plan3p := proc (A::list, B::list, C::list)
local d, M, N, P, Mat, Det, t, U, V;
M := `<,>`(x-A[1], B[1]-C[1], C[1]-A[1]); N := `<,>`(y-A[2], B[2]-C[2], C[2]-A[2]); P := `<,>`(z-A[3], B[3]-C[3], C[3]-A[3]);
Mat := Matrix([M, N, P]);
Det := LinearAlgebra:-Determinant(%);
d := igcd(coeff(Det, x), coeff(Det, y), coeff(Det, z), tcoeff(Det));
print(`Une équation cartésienne du plan est :`);
t := Det/d; print([t = 0]); print('Une*représentation*paramétrique*du*plan*est; -1');
U := A-B; V := B-C;
[x = lambda*U[1]+mu*V[1]+A[1], y = lambda*U[2]+mu*V[2]+A[2], z = lambda*U[3]+mu*V[3]+A[3]] end proc;
A := [-6, 3, -2]; B := [5, 2, 1]; C := [2, 5, 2];plan3p(A, B, C);
How to know if these procedures are correct or not. Thank you.

## How to find an orthogonal circle ? ...

We consider a fixed circle (C) tangent to a fixed line Δ at a given point O of this line.
Circles Γ tangent to circles C in M and to the right Δ in N are studied.
Show that the MN line passes through a fixed point I. Infer that the circles Γ remain orthogonal to a fixed circle.
My code is :
restart; with(geometry);with(plots);
_EnvHorizontalName := 'x';_EnvVerticalName := 'y';
dist := proc (M, N) sqrt(Vdot(expand(M-N), expand(M-N))) end proc;
point(oo, 0, 3); p := 6;
point(N, 5, 0);
line(Delta, y = 0, [x, y]);
para := x^2 = 2*p*y;
solve(subs(x = 5, para), y); point(varpi, 5, 25/12);
line(alpha, [oo, varpi]); k := 3/(25/12);
point(M, (0+5*k)/(1+k), (3+25*k*(1/12))/(1+k));
circle(C, x^2+(y-3)^2 = 9, [x, y]);cir := implicitplot(x^2+(y-3)^2 = 9, x = -5 .. 5, y = -5 .. 7, color = blue);
Para := implicitplot(para, x = -40 .. 40, y = 0 .. 40, linestyle = 3, color = coral);
homothety(J, N, -k, M); coordinates(J);
circle(C1, (y-25/12)^2+(x-5)^2 = (25/12)^2, [x, y]);line(lNJ, [N, J]);
triangle(T1, [J, oo, M]); triangle(T2, [N, varpi, M]);
C1 := implicitplot((y-25/12)^2+(x-5)^2 = (25/12)^2, x = 2 .. 8, y = 0 .. 5, color = magenta);dr1 := draw([oo, Delta, varpi, N, M, J], printtext = true); dr2 := draw([alpha(color = black), lNJ(color = black), T1(color = green, filled = true), T2(color = green, filled = true)]);
inversion(M, M, C);
inversion(N, M, C);
Fig := proc (xOm)
local cir, c2, C2, C1, c3, C3, k, M, N, J, sol, dr, varpi;
global p, para, Para;
sol := solve(subs(x = xOm, para), y);
cir := (y-sol)^2+(x-xOm)^2 = sol^2; c2 := x^2+(y-3)^2 = 9;
geometry:-point(N, xOm, 0); sol := solve(subs(x = xOm, para), y);
geometry:-point(varpi, xOm, sol); k := 3/sol;
geometry:-point(M, xOm*k/(k+1), (3+k*sol)/(k+1));
geometry:-homothety(J, N, -k, M);
c3 := (x-(1/2)*xOm)^2+(y-3)^2 = (1/4)*dist(N, J)^2;
C1 := plots:-implicitplot(cir, x = -xOm .. 3*xOm, y = 0 .. 3*xOm, color = magenta);
C2 := plots:-implicitplot(c2, x = -xOm .. 2*xOm, y = 0 .. 2*xOm, color = blue);
C3 := plots:-implicitplot(c3, x = -xOm .. 2*xOm, y = 0 .. 2*xOm, color = blue);
dr := geometry:-draw([varpi, M, J]);
plots:-display([Para, C2, C1, C3, dr], view = [-xOm .. 3*xOm, -1 .. 3*xOm], axes = normal, scaling = constrained) end proc;

Fig(8);
display([seq(Fig(4+.8*i), i = 4 .. 15)]);
display({C1, Para, cir, dr1, dr2}, view = [-8 .. 8, -1 .. 8], axes = normal, scaling = constrained, size = [500, 500]);
I don't know what is that orthogonal circle to each tangent circles. Thank you to help me.

.

## Bug in the combine command ...

Hi !

Sorry but there is a bug in the "combine" command when combining double summations.
Maple 2017,2018 and 2020 all give me a wrong answer. I have an old version of Maple which gives the correct answer.
I have put an example in the attached file.

bugcombine.mw

Best regards
Réjean

## Why Explore does't work ?...

restart;
with(plots); with(LinearAlgebra);
_EnvHorizontalName := 'x';

_EnvVerticalName := 'y';

x1,y1,x2,y2,x3,y3:=0,-3,3,1,5,-2:
A := [x1, y1]: B := [x2, y2]: C := [x3, y3]:

Barycentre := proc (A, B, t) description "Barycentre de 2 points A(1) et B(t) dans le rapport t";
return [(1-t)*A[1]+t*B[1], (1-t)*A[2]+t*B[2]] end proc;
ellip := proc (r1, r2) local a, b, c, d, e, f, D, E, F, eq1, eq2, eq3, eq4, eq5, eq6, x0, y0, EE, r3, sol, Ff, Tg;
global A, B, C;
r3 := -1/(r2*r1);
D := Barycentre(C, B, 1/(1-r1)); E := Barycentre(A, C, 1/(1-r2)); F := Barycentre(B, A, 1/(1-r3));
Ff := proc (x, y) options operator, arrow; a*x^2+2*b*x*y+c*y^2+2*d*x+2*e*y+f end proc;
Tg := proc (x0, y0, x, y) options operator, arrow; a*x*x0+b*(x*y0+y*x0)+c*y*y0+d*(x+x0)+e*(y+y0)+f end proc;
eq1 := Ff(D[1], D[2]);
eq2 := Ff(E[1], E[2]);
eq3 := Ff(F[1], F[2]);
eq4 := Tg(F[1], F[2], x1, y1);
eq5 := Tg(D[1], D[2], x2, y2);
eq6 := Tg(E[1], E[2], x3, y3);
sol := op(solve([eq1, eq2, eq3, eq4, eq5, eq6], [a, b, c, d, e]));
assign(sol);
EE := subs(f = 1, Ff(x, y) = 0) end proc;

ellip(-1, -7); tri := plot([A, B, C, A], color = blue):

po := plot([A, B, C], style = point, symbolsize = 15, symbol = solidcircle, color = red);
tp := textplot([[A[], "A"], [B[], "B"], [C[], "C"]], 'align' = {'above', 'left'});
x := 'x'; y := 'y';
ELL := seq(implicitplot(ellip(-7/11-(1/11)*j, -1/17-3*j*(1/17)), x = 0 .. 5, y = -3 .. 1, color = ColorTools:-Color([rand()/10^12, rand()/10^12, rand()/10^12])), j = 1 .. 17);
display([tri, ELL, po, tp], view = [-.5 .. 5.5, -4 .. 1.5], axes = none, scaling = constrained, size = [500, 500]);
Explore(implicitplot(ellip(r1, r2), x = 0 .. 5, y = -3 .. 1), parameters = [r1 = -2.18 .. -.7, r2 = -3 .. -.23]);
Can you tell me why this last instruction does't work ? Thank you.

## Tensor summation...

Hi, I have a problem with tensor calculus. Please guide me.

I have two Tensors B[mu, nu] and A[~mu, ~nu].

Furthermore, I have two mixed tensors as U[~1, mu, nu] and U[~2,mu,nu]

rho, mu, and nu can run from 1 to 2. Hence, A, B, and both Us are 2*2 matrices.

Note that there was only one U, but since it is a mixed tensor, hence I have separated it into two tensors for making it easy.

Now I want to compute the following summation:

U[~rho,mu,nu] U[~alpha,beta,gamma] B[rho,alpha] A[~mu,~beta] A[~nu,~gamma].

Maple must give a number for rho, mu, nu, alpha, beta, and gamma (which can take 1 and 2) and compute "all" possible summations. Since the result will be just "a number", hence I could not use TensorArray.

How can I do it and get a result?

The forms of all tensors are in the attached maple file:
question.mw

## Finding a conic tangents to 3 sites of a triangle ...

We consider a triangle ABC, its circumscribed circle (O), of radius R, its inscribed circle (I) of centre I. We designate by α, β, γ the points of contact of BC, CA, AB with the circle (I), by A', B', C' the points of meeting other than A, B, C, of AI, BI, CI with the circle (O), by the media of BC, CA, AB.
.Establish that there is a conic (E), focus I, tangent to βγ, γα, αβ.
My code :

restart;
with(geometry);
with(plots); _local(gamma);
_EnvHorizontalName := x; _EnvVerticalName := y;
alias(coor = coordinates);
point(A, -5, -5); point(B, 7, -1); point(C, 1, 5);
triangle(ABC, [A, B, C]); circumcircle(_O, ABC, 'centername' = OO); incircle(_I, ABC, 'centername' = Io);
line(lBC, [B, C]); sol := solve({Equation(_I), Equation(lBC)}, {x, y}); point(alpha, subs(sol, x), subs(sol, y));
line(lCA, [C, A]); sol := solve({Equation(_I), Equation(lCA)}, {x, y}); point(beta, subs(sol, x), subs(sol, y));
line(lAB, [A, B]); sol := solve({Equation(_I), Equation(lAB)}, {x, y}); point(gamma, subs(sol, x), subs(sol, y));
line(lAO, [A, OO]); intersection(Ap, lAO, lBC);
line(lBO, [B, OO]); intersection(Bp, lBO, lCA);
line(lCO, [C, OO]); intersection(Cp, lCO, lAB);
midpoint(l, B, C); midpoint(m, A, C); midpoint(n, A, B);
triangle(T, [alpha, beta, gamma]);
dr := draw([ABC(color = blue), _O(color = red), _I(color = magenta), lAO(color = black), lBO(color = black), lCO(color = black), T(color = red), alpha, beta, gamma, Ap, Bp, Cp, l, m, n], printtext = true);
display([dr], axes = normal, scaling = constrained, size = [800, 800]);
How to find the Equation of (E); Thank you.

 First 6 7 8 9 10 11 12 Last Page 8 of 61
﻿