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I get the wrong answer for the Derivative of Sin[x]

Posted 11 years ago
I used  
f[x_] = (x^3 + 2 x^2 + 15 x + x)*Sin[ Pi* x];         
Derivative [1][f]
gave a wrong answer.     The Derivative of  Sin x  is  Cos x  NOT zero. What is wrong?
POSTED BY: Jose Martinez
2 Replies
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POSTED BY: Moderation Team
Posted 11 years ago
I think you used for the derivation this expression:
D[f, x]
But the right expression must be like this: 
D[f[x], x]
POSTED BY: Teoman Ozturk
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