This can be done without loops as follows:

DetVanMat:=proc(A::list)

local B;

B:=combinat[choose]({seq(i, i=1..nops(A))}, 2);

mul(A[B[k,2]]-A[B[k,1]], k=1..nops(B));

end proc;

Example:

DetVanMat([seq(x[i], i=1..4)]);

      (x[2]-x[1])*(x[3]-x[1])*(x[4]-x[1])*(x[3]-x[2])*(x[4]-x[2])*(x[4]-x[3])

The procedure finds the Nth term of the sequence of lists defined by the recurrence

f(0)=[0., 0]

f(n)=[f(n-1)[1]+1/n, n]

in lines:

1)   ftn:=arg[1];

2)  srtpt:=args[2];

3)  print('please change another starting point');

4)  error solution 'not' found;  

Right-click on the animation and choose  Export As -> GIF .  The created file can look in any modern browser or player, or download here as below:

plots[animate](plot, [a*(2*x^3 + x^2 - 3*x), x=-2..2, thickness=2], a=1..10, frames=100 );

r :=t->(cos(t)+t*sin(t))*i+(sin(t)-t*cos(t))*j+5*k:

 D(r)(t);  # Vector T

r1 := t->(3*cos(t))*i+(3*sin(t))*j+2*t^(3/2)*k:

D(r1)(t):

 int(sqrt(coeff(%, i)^2+coeff(%, j)^2+coeff(%, k)^2), t=0..3);  # Length of the curve

                t cos(t) i + t sin(t) j

                           14

First, using the command  combinat [choose](A, 10) , you create a list of all subsets of A, containing 10 elements. Then, in a loop checking all these subsets.

A simple example: to find all the subsets of 5 elements of the set {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} such that the sum of their elements is 20.

Solution:

A:={seq(i, i=1..10)}:

L:=combinat[choose](A, 5):

S:=[]:

for k in L do

if add(k[i], i=1..5)=20 then S:=[op(S), k]: fi:

od:

S;

beta := 0.25:

alpha0 := 0.2580:

alphad := 0.545:

Bmax := 0.7:

Alpha := 0..Pi/2:

A := plot((1-beta-beta*cos((Pi*alpha)/(0.8*alpha0)))*Bmax, alpha=0..0.8*alpha0, color=red, thickness=3):

B := plot(Bmax, alpha=0.8*alpha0..alphad, color=blue, thickness=3): 

plots[display](A, B, scaling=constrained, view=[Alpha, -0.2..1]);

Markiyan Hirnyk

1) Why condition if ... end if?

restart; a(1) := 4; a(2) := -2; a(3) := 1; N := 50;

for n from 3 to N do  a(n+1) := a(n)-5*a(n-1)+a(n-2) end do: a(N);

2) Your code is slower in 2 - 3 times. Compare for N = 100000.

a:=4:  b:=-2:  c:=1:

for i to 47 do

d:=c:  c:=d-5*b+a:  a:=b:  b:=d:

od:

c;

             43463309239573150

a:=n->((-1)^(n+1)+4*n-1)/2:

seq(a(n), n=1..8);

           2, 3, 6, 7, 10, 11, 14, 15

eliminate({x-lambda*p=0, y-lambda=0}, lambda):

p=solve(op(%[2]), p);

           p=x/y

Example:

S:={[1, 1], [2, 1], [2, 2], [3, 1], [3,2]}:

f:=proc(x,y)

x^2+y^2:

end proc:

seq(f(op(S[i])), i=1..nops(S));

              2, 5, 8, 10, 13

If you frequently use the symbol perpendicularity it makes sense to write a special procedure. Formal arguments: L - a list of the coordinates of the center of the character, l - length of a stick, th - thickness, c - color, alpha - angle of the vertical stick from the positive direction of the horizontal axis.

PerpSymb:=proc(L, l, th, c, alpha)

local A, B;

uses plottools;

A:=line(L,[L[1]+l*cos(alpha), L[2]+l*sin(alpha)], color=c, thickness=th);

B:=line([L[1]-l*sin(alpha)/2, L[2]+l*cos(alpha)/2], [L[1]+l*sin(alpha)/2, L[2]-l*cos(alpha)/2], color=c, thickness=th);

A, B;

end proc;

Example:

plots[display](PerpSymb([1,0.7], 0.15, 2, red, 2*Pi/3), PerpSymb([1.5,1], 0.2, 4, black, Pi/2), PerpSymb([2,0.7], 0.25, 6, blue, Pi/3), view=[0..3, 0..2], scaling=constrained);

with(LinearAlgebra):

do M:=RandomMatrix(3, 3, generator=1..9):

if Determinant(M)<>0 then break: fi:

od:

v:=RandomVector(3, generator=1..9):

'M'=M, 'v'=v;

x=LinearSolve(M, v);

The easiest way to solve this problem is by generating functions, noting that the number of integer and positive roots of the equation is the number of non-negative integer roots of the equation

2a +3 b +10 c = 2010 - (2 +3 +10) = 1995

coeff(convert(series(1/(1-x^2)/(1-x^3)/(1-x^10),  x=0,  1996), polynom),  x^1995);

                                                              33367

The problem can be also solved programmatically as follows:

restart:

n:=0:

for a from 1 to floor(2010/2) do

for b from 1 to floor((2010-2*a)/3) do

for c from 1 to floor((2010-2*a-3*b)/10) do

if 2*a+3*b+10*c=2010 then n:=n+1: fi:

od: od: od:

n;

                                                       33367