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July 29, 2016
Posted by **Mary** on Wednesday, March 20, 2013 at 4:42pm.

f(cos x) if f'(x)= 1/x

find (f(cos x))'

i got tan x sec x

this is wrong.

please explain. thank you

- Derivative -
**Steve**, Wednesday, March 20, 2013 at 5:18pmif f'(x) = 1/x

f(cos x)' = 1/cosx * -sinx = -tanx