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# scalar functions watch

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1. this could be quite a silly questions but
the vector r = (x,y,z) so |r|=sqrt(x^2 +y^2 +z^2)

f=|r|^n
the derivative = n| r |^(n-2) x r

why does the derivative have n-2 and not n-1?
2. (Original post by STLS)
this could be quite a silly questions but
the vector r = (x,y,z) so |r|=sqrt(x^2 +y^2 +z^2)

f=|r|^n
the derivative = n| r |^(n-2) x r

why does the derivative have n-2 and not n-1?
if you write as you will see that when the expression is differentiated, the n/2 term becomes (n/2)-1 = (n-2)/2.

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