Re: defining an unknown function
- To: mathgroup at smc.vnet.net
- Subject: [mg129451] Re: defining an unknown function
- From: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>
- Date: Mon, 14 Jan 2013 23:30:45 -0500 (EST)
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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 e-vals and e-vecs. 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.
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