variation - Compute the variation
Calling sequence:
variation(expr,var,dvar)
Parameters
expr - An expression containing the variables in var.
var - A variable, or a list of variables, to perform the variation with respect to.
dvar - the names of the variations of the variables in var. Must have same length as var
Synopsis:
Examples:
> J:=ElementInt(u(x)^2);
2
J := ElementInt(u(x) )
> variation( J , u(x),du(x));
ElementInt(2 u(x) du(x))
> F:=ElementInt(u(x,y)^2 + v(x,y)^2);
2 2
F := ElementInt(u(x, y) + v(x, y) )
> variation(F,[u(x,y),v(x,y)],[du(x,y),dv(x,y)]);
ElementInt(2 u(x, y) du(x, y)) + ElementInt(2 v(x, y) dv(x, y))
> BClist:=[u(x)=0,diff(u(x),x)=q];
d
BClist := [u(x) = 0, -- u(x) = q]
dx
> variation(BClist,u(x),du(x));
d
[du(x) = 0, -- du(x) = 0]
dx