EugeneKalentev

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4 years, 180 days

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These are questions asked by EugeneKalentev

Hello. Is there a built-in function to determine the required sample size for different distributions in a population?

Hello.
I can not find a tool for calculating the number of permutations with fixed points. I looked at the package combinat. Help me please.

 

restart

int(sin(x), x)

-cos(x)

(1)

int(x^2, x)

x^2*_X

(2)

``

 

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Hello everyone.

Tell me how to solve this equation grad(div(f(x,y,z)))+K*Laplacian(f(x,y,z))=0

Here, the function f defines a vector field.

I tried so

restart

with(Physics[Vectors]):

Physics:-Vectors:-Setup(mathematicalnotation = true)

[mathematicalnotation = true]

(1)

eq := Gradient(Divergence(f(x, y, z)))+K*Laplacian(f(x, y, z)) = 0

Error, (in Physics:-Vectors:-Nabla) Physics:-Vectors:-Divergence expected a vector function, but received the scalar function: f(x, y, z)

 

``


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Hello everyone. 

I can not calculate it here


restart

with(VectorCalculus):

with(plots):

v1 := x^2+y+`-`(sin(z))

x^2+y-sin(z)

(1)

v2 := VectorCalculus:-`+`(VectorCalculus:-`+`(x^2, 1/y), VectorCalculus:-`-`(VectorCalculus:-`*`(2, z)))

x^2+1/y-2*z

(2)

v3 := VectorCalculus:-`+`(VectorCalculus:-`+`(VectorCalculus:-`*`(3, x), y^2), z)

y^2+3*x+z

(3)

vv := VectorField(`<,>`(v1, v2, v3), 'cartesian'[x, y, z])

Vector[column](%id = 18446744074235504150)

(4)

fieldplot3d(vv, x = -1 .. 1, y = -1 .. 1, z = -1 .. 1, arrows = `3-D`, grid = [5, 5, 5], axes = normal)

 

Flux(vv, Sphere(`<,>`(0, 0, 0), r))

Error, (in sprintf) Maple was unable to allocate enough memory to complete this computation.  Please see ?alloc

 

 

``


Probably, the problem with the calculation of surface integrals. I would be grateful for any help.

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