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Sigmoid Function

Hello all,
Sigmoid Function or Logistic Function , it is used in Machine Learning problems for the purpose of learning (Neural network ) on curves.
its range between ]0,1[ it is horizontal asymptotic on 0 and 1, because of its range between 0 and 1 it is used in classification using threshold for example if we take 0.5 as a threshold  values greater than 0.5 are considered Ones and  values less than or Equal  0.5 considered 0.

it has the following formula :


  and it shape as following :
from wikipedia 
so it accept differentiation over its domain unlike Step Function.

differentiation of sigmoid function : 

I finished the article , i hope you understand it .
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