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Old 05-07-2012, 03:13 AM
IamMrBB IamMrBB is offline
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Default Re: clarification on lecture 9

The formula on the slide is correct.

d/dx (ln(1+exp(-f(x))) = -exp(-f(x))f'(x)/(1+exp(-f(x))

now multiply both numerator and denominator with exp(f(x)) and the right formula -f'(x)/(exp(f(x))+1) follows since exp(f(x))*exp(-f(x)) = 1
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