Pytorch Sigmoid Function what is e
I have a question on setting up the sigmoid function in pytroch. 

So I define it as this

# Sigmoid function
def sigmoid(x):
    return 1/(1 + torch.exp(-x))


But then looking at the sigmoid function from here http://mathworld.wolfram.com/SigmoidFunction.html

The sigmoid should be defined as

y = 1/(1 + e^-x)


I see the 1/(1+  part but I don't get the e^-x part. Can someone explain why 

torch.exp(-x) == e^-x 


What is e here? Is that the tensor. But i thought that x was the tensor

Here e is the exponential constant e and 
torch.exp(-x) == e^-x


torch.exp(x) returns e^x

