
Re: How to calculate the partial derivative?
Posted:
Nov 22, 2012 4:40 AM


repl = {L1 > a1 + b1*x + c1*y, L2 > a2 + b2*x + c2*y, L3 > a3 + b3*x + c3*y};
SetOptions[D, NonConstants > {L1, L2, L3}];
NN = L1*L2;
DNex = D[NN, x] /. D[repl, x]
b2 L1 + b1 L2
DNex /. repl
b2 (a1 + b1 x + c1 y) + b1 (a2 + b2 x + c2 y)
Bob Hanlon
On Wed, Nov 21, 2012 at 7:48 PM, Tang Laoya <tanglaoya1989@gmail.com> wrote: > Dear all, > > I am trying to calculate the partial derivative by mathematica, I have the following commands: > L1=a1+b1*x+c1*y; > L2=a2+b2*x+c2*y; > L3=a3+b3*x+c3*y; > > NN=L1*L2; > > DNx=D[NN,x]; > > I got the following result: > DNex=b2 (a1+b1 x+c1 y)+b1 (a2+b2 x+c2 y) > > How to do to have the following result? > > DNex=b2*L1 + b1 * L2 > > > Thanks, > Tang Laoya >

