    Sentence 1: What is the sigmoid function, and  what is its use in machine Learning's neural  networks?    Sentence 2: In machine learning algorithms,  why is sigmoid function used primagily and  not functions Like tanh(x)? In tanh® for eg.  seem to split y-axis evenly and flatten out  fast as x approaches +/- infinit¥. The range  being: sigmoid [0-1] and tanh(x) [-1,1].    at