Help me expand a multivariable differential equation in maple

[billano786]

I wish to expand a multivariable differential equation in maple, the code is below

f:=sin(x(t)+y(t))+x(t)+diff(x(t),t);
/d \
f := sin(x(t) + y(t)) + x(t) + |-- x(t)|
\dt /

> mtaylor(f,{x(t)=1,y(t)=-2},5);
Error, (in mtaylor) invalid 2nd argument (expansion point)

Can any one help in writing the correct code?

 

[electricpete]

Re: Need help in maple

I'm no expert in multivariate Taylor expansions. But I think the maybe the diff(x(t),t) is giving problems... perhaps it is an ill-posed problem.

If you get rid of that, it works.
readlib(mtaylor):
f:=sin(x+y)+x+z;
mtaylor(f,[x=1,y=-2],5);
returns a result.

 

[billano786]

Re: Need help in maple

I know that by removing the derivative i can get expansion, however, my problem is to expand a multivariable differential equation.