Using part of output of an expression as a input of another expression
Subject: Using part of output of an expression as a input of another expression
From: Cuneyt Ertal
Date: Thu, 7 Jan 2010 10:18:43 +0200
Hi I am a newbie maxima user. I want to use part of an output expression as
a input of another expression.
(%i3) w(x,t):=sum(w[n](t)*sin(n*%pi*x),n,0,inf);
(%o3) w(x,t):=sum(w[n](t)*sin(n*%pi*x),n,0,inf)
(%i4) diff(w(x,t),x);
(%o4) %pi*sum(n*w[n](t)*cos(%pi*n*x),n,0,inf)
(%i5) diff(w(x,t),x,2);
(%o5) -%pi^2*sum(n^2*w[n](t)*sin(%pi*n*x),n,0,inf)
(%i6) diff(w(x,t),x,3);
(%o6) -%pi^3*sum(n^3*w[n](t)*cos(%pi*n*x),n,0,inf)
(%i7) diff(w(x,t),x,4);
(%o7) %pi^4*sum(n^4*w[n](t)*sin(%pi*n*x),n,0,inf)
(%i8) diff(w(x,t),t,2);
(%o8) sum(('diff(w[n](t),t,2))*sin(%pi*n*x),n,0,inf)
(%i9) f(x,t):=sum(f[n](t)*sin(n*%pi*x),n,0,inf);
(%o9) f(x,t):=sum(f[n](t)*sin(n*%pi*x),n,0,inf)
(%i10) diff(f(x,t),x,2);
(%o10) -%pi^2*sum(n^2*f[n](t)*sin(%pi*n*x),n,0,inf)
(%i11) diff(w(x,t),x,4)+diff(w(x,t),t,2)=sum(f[n](t)*sin(n*%pi*x),n,0,inf);
(%o11)
(sum(('diff(w[n](t),t,2))*sin(%pi*n*x),n,0,inf))+%pi^4*sum(n^4*w[n](t)*sin(%pi*n*x),n,0,inf)=sum(f[n](t)*sin(%pi*n*x),n,0,inf)
i want to use %o11 without sums , like this;
'diff(w[n](t),t,2)*sin(%pi*n*x)+%pi^4*(n^4*w[n](t)*sin(%pi*n*x)=f[n](t)*sin(%pi*n*x)
How can I do that?
--
Cuneyt Ertal.