## Surface area of a Torus...

I am attempting to find the surface area of a Torus. I can create a graph very easily, but am struggling with the SurfaceArea command. The code reads so far:

(Inputting the given function for the torus):

> r := (phi,theta) -> <(cos(phi)+3)*cos(theta),(cos(phi)+3)*sin(theta),sin(phi)>:

'r(phi,theta)' = r(phi,theta);

(Generating a graph of the torus):

>plot3d(r(phi,theta),phi=0..2*Pi,theta=0..2*Pi,scaling=constrained);

(SurfaceArea command):

>SurfaceArea(r(phi,theta),phi=0..2*pi,theta=0..2*pi);

I am very new to the program so the solution may be obvious. Any suggestions on how to go about it?

## Need help plotting a vector field using fieldplot3...

Hello, I am attempting to plot a vector field in Maple. I have the following code so far:

SetCoordinates('cartesian'[x,y,z]):

F := VectorField(<y*z*e^(x*y*z)+3*x^(2),x*z*e^(x*y*z)+2*y*z+cos(y),x*y*e^(x*y*z)+y^(2)+1>);

I am struggling with the fieldplot3d commands, as I am supposed to plot it in the box -1<=x,y,z<=1. How do I go about inserting these bounds?

## How to get rid of the ERROR: Warning, solutions ma...

I am not very familiar with maple.

Kindly help me fix the error.

I want to solve the three equations- eq1, eq2 and eq3 simultaneously by equating to zero, i.e.,

eq1= eq2= eq3= 0, to find the values of the 3 variables t[1], t[2], xi

FINAL2.mw

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solve({eq1, eq2, eq3}, {xi, t[1], t[2]});

Warning, solutions may have been lost

## Solving nonlinear equation with fsolve...

Hi guys

I'm trying to solve this equation

eqns := {(1-sin(b_u)*sin(s)/(cos(b_u-y_f)*cos(s-y_f)))*(1/cos(s-y_f)^2-1/sin(s)^2) = -(cot(s)+tan(s-y_f)+Z)*sin(b_u)*(cos(s)/cos(s-y_f)+sin(s)*sin(s-y_f)/cos(s-y_f)^2)/cos(b_u-y_f)}

where

b_u = 1/tan(0.8)
Z = 892/(27417000*f_z)
y_f = 9*Pi/180

I have a bondary condition where s=s_0 and s_0 = (1/4)*Pi-1/2*(b_u-y_f)

And i want to solve this nonlinear equation from f_z=0.00005 to f_z=0.0005 by interval 0.000001 interval

I have tryed using this topic as an example

https://www.mapleprimes.com/questions/200995-Solve-By-Newton-Raphson-Method

But in the final i'm surprised with the error "Error, (in fsolve) initial approximation does not evaluate to float"

Thanks

## Piecewise function - How plot function with piece...

Hi

I have the following piecewise function in Maple:

`sigmaP:=piecewise(u < -1,-1,u >1,1,u);`

Now we can plot this function:

`plot(sigmaP,u=-5..5,size=[1200,300],gridlines,discont=[showremovable]);`

Next, I define a new piecewise  function as

`sigmaF:=u->piecewise(u < -1,-1,u >1,1,u);`

and I use this function in

```Fun:=proc(x1,x2,u1,u2)
2*x1*(1+x2)*sigmaF(u1)+(1+x2^2)*sigmaF(u2);
end proc:```

Now I need to find a minimum of this function so I use the following code

`GlobalOptimization:-GlobalSolve(Fun,x1,x2,u1,u2);`

where

```x1:=-5..5;
x2:=-10..100;
u1:=-1..1;
u2:=-1..1;
```

And I have the problem with plot function Fun. How to plot function Fun???

Best

Hello,

 >
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## Unable to plot" kx" vs "f "(maple code attached).....

range of "kx" variable [0 to 8x106] and range of "f" variable  [80x1012 to 220x1012]

## Why different between calculate two form? ...

Why different between calculate two form? I use maple 2017

evalf(sech(20)^2); evalf(sech(-20)^2);

1.699341702 *10^ -17

1.699341702 *10^ -17
evalf(1-tanh(20)^2); evalf(1-tanh(-20)^2);
0.
0.

## what is the meaning of % ?...

i want to calculate the eigenvalues and eigenvectors of two matrices ,i get these results, can anyone explain to me the meaning ?

A:=linalg[matrix](3,3,[-1,2,0,4,-2,3,0,1,-3]);
> B:=linalg[matrix](3,3,[2,0,1,4,-1,1,2,0,-5]);

> eigenvalues(A);

8                                    4
1/2 %2 + -------------------- - 2, - 1/4 %2 - --------------------
1/2 1/3                              1/2 1/3
(20 + 4 I 231   )                    (20 + 4 I 231   )

1/2 /                  8          \
- 2 + 1/2 I 3    |1/2 %2 - --------------------|, - 1/4 %2
|                      1/2 1/3|
\         (20 + 4 I 231   )   /

4
- -------------------- - 2
1/2 1/3
(20 + 4 I 231   )

1/2 /                  8          \
- 1/2 I 3    |1/2 %2 - --------------------|
|                      1/2 1/3|
\         (20 + 4 I 231   )   /

1
%1 := --------------------
1/2 1/3
(20 + 4 I 231   )

1/2 1/3
%2 := (20 + 4 I 231   )

eigenvectors(B);
1/2      [            1/2  65          1/2   ]
[- 3/2 + 1/2 57   , 1, {[7/4 + 1/4 57   , -- + 9/28 57   , 1]}],
[                 28                ]

1/2      [            1/2  65          1/2   ]
[- 3/2 - 1/2 57   , 1, {[7/4 - 1/4 57   , -- - 9/28 57   , 1]}],
[                 28                ]

[-1, 1, {[0, 1, 0]}]

## what is the diffrence ?...

such a list H:=
[0, 4, 8, 1, 2, 1, 4, 2, 8]

what is the diffrence between these 2 commands ? has(H,integer), type(H,integer);

## how to get this sequence ?...

how to obtain the sequence of sin(((Kπ)/4)), where the integer K  is varying from 1 to 8, and then to delete the zeros.

## Is this the true result ?...

i'm triying to solve this sytem ,

solve({x^2+y^2=3,x^2+2*y^2=3},{x,y});
{y = 0, x = RootOf(_Z^2-3)}
what is the meaning of RootOf

maple gives me this, can anyone explain to me,the signification of the solutions ?

## Solution of second order differential equation...

Dear Users!

Hope you would be fine with everying. I want to solve the following 2nd order linear differential equation.

(1+B)*(diff(theta(eta), eta, eta))+C*A*(diff(theta(eta), eta)) = 0;
where A is given as

A := -(alpha*exp(-sqrt((omega+1)*omega*(M^2+alpha+1))*eta/(omega+1))*omega+alpha*exp(-sqrt((omega+1)*omega*(M^2+alpha+1))*eta/(omega+1))+exp(-sqrt((omega+1)*omega*(M^2+alpha+1))*eta/(omega+1))*omega-alpha*omega+exp(-sqrt((omega+1)*omega*(M^2+alpha+1))*eta/(omega+1))-alpha-omega-1)/sqrt((omega+1)*omega*(M^2+alpha+1));
I want solution for any values of omega, alpha, M, B, C and L. The BCs are below:

BCs := (D(theta))(0) = -1, theta(L) = 0.

## how can i obtain this ?...

Write a command maple to count each two elements distincts of a list L ?

## Error, (in unknown) invalid arguments to divide: 4...

Hello,

There is a error happened when i use the command "eliminate" ,

And,the target two equations is:

[190.0315457*d^6-7.601261828*d^4+344.0*c^2*d^2-2.677685950*c^4, 0.6830134554e-2*c^4+2084.317025*d^8-166.7453620*d^6+3.334907240*d^4-c^2*d^2]

The error is happened like that shown below.

Error, (in unknown) invalid arguments to divide: 4903.60312, 1.000000000 to use eliminate command!

I wonder why this error happened, could anyone help me!

Thanks!!!

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