
Re: defining an unknown function
Posted:
Jan 14, 2013 11:28 PM


Hi all, I would like to start by defining H = {{\partial_{x,x} L,\partial_{x,y} L}, {\partial_{y,x} L, \partial_{y,y}L}}; where at this stage, the only think i know is that L is of the form L(x,y). This is a Hessian, and I would like to symbolically compute the evals and evecs. I wanted to know how I should tell mathematica to consider L as L(x,y) ?
Thanks, Sid.
Hi, Sid,
Is this:
H[f_]:=Det[{{D[f,{x,2}],D[D[f,x],y]},{D[D[f,y],x],D[f,{y,2}]}}]//Simplify;
H[Sin[x*y]]
Cos[x y] (Cos[x y]+2 x y Sin[x y])
the function that you mean?
Have fun, Alexei
Alexei BOULBITCH, Dr., habil. IEE S.A. ZAE Weiergewan, 11, rue Edmond Reuter, L5326 Contern, LUXEMBOURG
Office phone : +35224542566 Office fax: +35224543566 mobile phone: +49 151 52 40 66 44
email: alexei.boulbitch@iee.lu<mailto:alexei.boulbitch@iee.lu>

