## 20 Reputation

8 years, 288 days

## thats not the problem...

i changed and still doesnt work@tomleslie

## thank you very much...

@tomleslie  that was of a great help since the first answer you provide you directed me to the right way

## thank you vey much...

@tomleslie  but i still have a problem with the results themselves they are so big and going bigger each time i hit enter

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 >
 > p:=Array(0..10):   p[0]:=0:   for i from 0 to 9 do       p[i+1]:=(u__doubledot[i+1]*(1))+(u__dot[i+1]*(3))+(u[i+1]*(2)):       phat[i+1]:= p[i+1]+((6)*u[i])+((7)*u__dot[i])+((8)*u__doubledot[i]):       u[i+1]:= phat[i+1]/(2):       u__dot[i+1]:=(u[i+1]/(2))-u[i]:       u__doubledot[i+1]:= (4*(u[i+1]-u[i])/(4)^2)-(4*u__dot[i+1]/(4))-(u__doubledot[i]):   end do;
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## now i got it thank u...

@Ronan thank u very much

## i did as u said but...

 >
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 >
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 > diff((2), y);
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 > diff((3), y);
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 >
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 > diff((5), x);
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 > diff((6), x);
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 >
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 > diff((8), x);
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 > diff((9), y);
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 > -(1/16)*sin((1/4)*Pi*x)*Pi^2*(c__1*cosh((1/4)*Pi*y)+c*`2`*sinh((1/4)*Pi*y)+c__3*y*cosh((1/4)*Pi/y)+c__4*y*sinh((1/4)*Pi*y));
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 > eval( (12), [x = 0]);
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 >
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 > eval( (14), [x = 20]);
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 >
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 > eval( (16), [y = 9]);
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 > evalf[5]( (17) );
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 >
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 > eval( (19), [y = -9]);
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 > evalf[5]( (20) );
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 >
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 > eval( (22), [y = 9]);
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 > evalf[5]( (23) );
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 >
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 > eval( (25), [y = -9]);
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 > evalf[5]( (26) );
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 > s:=solve({(sin.78540*x)*(362.25*c__1-362.25*c*`2`-0.84938e-3*c__3+4182.6*c__4) = -1.*sin(.25000*Pi*x),.78540*cos(.78540*x)*(461.22*c__1+461.22*c*`2`+.99617*c__3+4738.2*c__4) = 0,.78540*cos(.78540*x)*(-461.22*c__1+461.22*c*`2`+.99617*c__3-4738.2*c__4) = 0,sin(.78540*x)*(362.25*c__1+362.25*c*`2`+0.84938e-3*c__3+4182.6*c__4 = 0},{c1,c2,c3,c4,x});
 >

## Thank you...

Thank you very much

## i tried and got this error i think its b...

phi := sin(alpha*X)*(c1*cosh(alpha*Y)+c2*sinh(alpha*Y)+c3*Y*cosh(alpha*Y)+c4*Y*sinh(alpha*Y));
sin(alpha X) (c1 cosh(alpha Y) + c2 sinh(alpha Y)

+ c3 Y cosh(alpha Y) + c4 Y sinh(alpha Y))
alpha := (1/4)*pi;
1
- pi
4
`&sigma;X` := diff(phi, Y, Y);
/1 \ /1 /1 \ 2 1 /1 \ 2
sin|- pi X| |-- c1 cosh|- pi Y| pi + -- c2 sinh|- pi Y| pi
\4 / \16 \4 / 16 \4 /

1 /1 \ 1 /1 \ 2
+ - c3 sinh|- pi Y| pi + -- c3 Y cosh|- pi Y| pi
2 \4 / 16 \4 /

1 /1 \ 1 /1 \ 2\
+ - c4 cosh|- pi Y| pi + -- c4 Y sinh|- pi Y| pi |
2 \4 / 16 \4 / /
sigmaY := diff(phi, X, X);
1 /1 \ 2 / /1 \ /1 \
- -- sin|- pi X| pi |c1 cosh|- pi Y| + c2 sinh|- pi Y|
16 \4 / \ \4 / \4 /

/1 \ /1 \\
+ c3 Y cosh|- pi Y| + c4 Y sinh|- pi Y||
\4 / \4 //
sigmaXY := -(diff(phi, X, Y));
1 /1 \ /1 /1 \ 1 /1 \
- - cos|- pi X| pi |- c1 sinh|- pi Y| pi + - c2 cosh|- pi Y| pi
4 \4 / \4 \4 / 4 \4 /

/1 \ 1 /1 \ /1 \
+ c3 cosh|- pi Y| + - c3 Y sinh|- pi Y| pi + c4 sinh|- pi Y|
\4 / 4 \4 / \4 /

1 /1 \ \
+ - c4 Y cosh|- pi Y| pi|
4 \4 / /
B.Cs1(x = 0, `&sigma;x` = 0, x = 20, `&sigma;x` = 0);
B . (Cs1(x = 0, &sigma;x = 0, x = 20, &sigma;x = 0))
B.Cs2(y = 9, sigmaXY = 0, sigmaY = 0);
/ / 1 /1 \ /1 /1 \
B . |Cs2|y = 9, - - cos|- pi X| pi |- c1 sinh|- pi Y| pi
\ \ 4 \4 / \4 \4 /

1 /1 \ /1 \
+ - c2 cosh|- pi Y| pi + c3 cosh|- pi Y|
4 \4 / \4 /

1 /1 \ /1 \
+ - c3 Y sinh|- pi Y| pi + c4 sinh|- pi Y|
4 \4 / \4 /

1 /1 \ \ 1 /1 \ 2 / /1
+ - c4 Y cosh|- pi Y| pi| = 0, - -- sin|- pi X| pi |c1 cosh|- pi Y
4 \4 / / 16 \4 / \ \4

\ /1 \ /1 \ /1 \\
| + c2 sinh|- pi Y| + c3 Y cosh|- pi Y| + c4 Y sinh|- pi Y|| = 0
/ \4 / \4 / \4 //

\\
||
//
B.cs3(y = -9, `&sigma;XY` = 0, y = -9, sigmaY = sin((1/4)*pi*x));
/ / 1 /1 \ 2 /
B . |cs3|y = -9, &sigma;XY = 0, y = -9, - -- sin|- pi X| pi |c1
\ \ 16 \4 / \

/1 \ /1 \ /1 \
cosh|- pi Y| + c2 sinh|- pi Y| + c3 Y cosh|- pi Y|
\4 / \4 / \4 /

/1 \\ /1 \\\
+ c4 Y sinh|- pi Y|| = sin|- pi x|||
\4 // \4 ///
solve := phi, B.cs1, Bcs2, Bcs3;
Error, attempting to assign to `solve` which is protected. Try declaring `local solve`; see ?protect for details.

Thanks @Kitonum

## if I need to plot 2d at t=2...

What if I want to plot it in 2d

## Thank you...

Thank you very much.

## it is zero otherwise...

Zero otherwise.

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