Here you can find my proof of the sigmoid derivative.
https://drive.google.com/file/d/1GI-tA7UlNTUBf4rsLhpWCt1YnhT44o8l/view?usp=sharing
Here you can find my proof of the sigmoid derivative.
https://drive.google.com/file/d/1GI-tA7UlNTUBf4rsLhpWCt1YnhT44o8l/view?usp=sharing