MaplePrimes - answers and comments on Question, work around for a problem in dsolve, numeric?

A workaround

alec — Sun, 11 Sep 2005 21:23:03 Z

Here is a workaround,

k[0]:=t->(1+t)*t^2*cos(t);

sol1:=dsolve({diff(y(t),t)=-k[0](t-1),y(0)=k[0](0)},y(t),
numeric, output=listprocedure):

k[1]:=rhs(sol1[2]):

k1:=t->k[1](t-1):

plot([[t,k[0](t),t=-1..0],[t,k[1](t),t=0..1]],color=blue);

sol2:=dsolve({diff(y(t),t)=-'k1'(t),y(1)=k[1](1)},y(t),
numeric, output=listprocedure):

k[2]:=rhs(sol2[2]):

plot([[t,k[0](t),t=-1..0],[t,k[1](t),t=0..1],
[t,k[2](t),t=1..2]],color=blue);

Two more workarounds

alec — Mon, 12 Sep 2005 04:42:33 Z

Also, it can be done by adding known=k[1] in the dsolve command, i.e. changing the definition of sol2 in the original post to

sol2:=dsolve({diff(y(t),t)=-k[1](t-1),y(1)=k[1](1)},y(t),
numeric, output=listprocedure,known=k[1]):

One more workaround is in replacing k[1](t-1) in the same line with 'apply'(k[1],t-1), i.e. define sol2 as

sol2:=dsolve({diff(y(t),t)=-'apply'(k[1],t-1),y(1)=k[1](1)},y(t),
numeric, output=listprocedure);