I'm new to Mathematica, and I'm still learning. I'm trying to code this partial differentiation. Can someone please help me find out where I coded wrong? I've attached a hand-written solution below.
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- 1$\begingroup$ Please post your code, not images. Thanks. $\endgroup$Rohit Namjoshi– Rohit Namjoshi2020-04-19 00:30:24 +00:00Commented Apr 19, 2020 at 0:30
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1 Answer
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D[x1Com,x[1,i]] will give zero, since there is no x[1,i] any more in x1Com. There is only x[1,1] and x[1,2] and so on.
One way could be
ClearAll[x1Com, x, m]; x1Com = HoldForm@(Sum[(m[1, i]*x[1, i]), {i, 1, 6}]/Sum[m[1, i], {i, 1, 6}]) 
Now make a function to differentiate w.r.t. to specific x[1,i]
diff[x1Com_, x_] := D[ReleaseHold@x1Com, x]; Now use it
diff[x1Com, x[1, 1]] 
diff[x1Com, x[1, 2]] 
And so on.
