Incoherent value for partial derivative
- To: mathgroup at smc.vnet.net
- Subject: [mg91050] Incoherent value for partial derivative
- From: Miguel <misvrne at gmail.com>
- Date: Mon, 4 Aug 2008 03:26:32 -0400 (EDT)
Let In[1]: g[x_]:=3x^2+5x; FullForm[g'[x]] Out[1]: Plus[5,Times[6,x]] In[2]: g'[2] Out[2]: 17 Mathematica works fine and the result is correct. First, it executes the derivation and then the delayed substitution/assignation. But for partial derivative Mathematica works different way (not correspondig to FullForm In[3]: f[x_,y_]:=x^2+x y^2; FullForm[\!\( \*SubscriptBox[\(\[PartialD]\), \(x\)]\ \(f[x, y]\)\)] Out[3]: Plus[Times[2,x],Power[y,2]] In[4]: \!\( \*SubscriptBox[\(\[PartialD]\), \(x\)]\ \(f[1, 2]\)\) Out[4]: 0 I dont understand the reason.