Sigmoid
Domain: Math & Logic for AI
🎯 Motivation
Squashes any real number into (0, 1). Historically popular, now mostly replaced by ReLU in hidden layers.
📋 Concrete Example
Sigmoid(0) = 0.5. Very positive input goes to ~1, very negative goes to ~0.
🔗 Analogy
Like a dimmer switch smoothly going from off (0) to fully on (1).