zlacker

>>qqqqqu+(OP)
The mathematics of training a neural network. I understand how they work once trained, but that you can train them almost seems too good to be true.

>>elgfar+6t
You likely understand minimizing a continuously differentiable function. Now, you are minimizing a continuously differentiable error function (which measures the difference between the output of your hypothesis function and actual data), with respect to adjustable weights and biases that determine the value for the neurons going from one layer to the next. The complexity is in that the hypothesis function is a composition of many functions due to the layering, and there usually are a large number of neurons. However, you are basically doing the same thing many times.