fsenkel1

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14 years, 246 days

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These are answers submitted by fsenkel1

Thank you for your help. I looks like I need to review this material, it's been a few years....

Thanks,

 

Frank

I think the original form works, but you just get eigenfunctions of sin(beta*L) = 0...see below...after doing it by hand, it appears that some of the reasoning might be too complicated for Maple to work out, plus there are some implicit assumptions used...

Y_diffEq:=diff(y(x),x$4)-beta^4*y(x)=0;
#Y_BCs:=y(0)=0, (D@@2)(y)(0)=0, y(L)=0, (D@@2)(y)(L)=0;
ans_Y:=dsolve(Y_diffEq,y(x));


#Maples answer is messy, and convert doesn't give what I want so use form below
ans_Y:=A*sin(beta*x)+B*cos(beta*x)+C*sinh(beta*x)+D*cosh(beta*x);
Y_check:=diff(ans_Y,x$4)-beta^4*ans_Y=0;
simplify(%);


#BC at x=0
eval(ans_Y=0,x=0);
eval(diff(ans_Y,x$2)=0,x=0);


#so B = 0 and D = 0
#BC at x=L
eval(ans_Y=0,{x=L,B=0,D=0});
eval(diff(ans_Y,x$2)=0,{x=L,B=0,D=0});


#So C = 0 and eigenvalues are sin(beta*L) = 0



I didn't realize there was a difference. I copied a help example for the indexing..same for the backquote.

Thanks again.

I just went back and checked, the problem occurs with "Extended" typesetting, but displays as you would expect with "Maple Standard" typesetting. Thank you for resolving my problem. Out of curiosity, how did you know to look there? It never would have occured to me....

This appears to be a bug, I'll have to dig around to see how to communicate this to Maple.

Thanks again for the help

When I run the input above, the Matrix returns without the substitutions being shown. I think they have occured, but are not displayed?

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