Some typos and advices

[wyz]

I just finished course one. I really enjoyed it. I also found some unimportant typos.

• Week 4 reading material’s title:
  
  
• Week 4: Clarification: What does this have to do with the brain?
  
  
  
  I think it should be W transpose.
• Advice
  I strongly recommend that the following explanation about np.dot and np.sum be put before W2A2’s propagate function in advance.
  
  

[Mubsi]

Hey @wyz, thank you for sharing these and taking our course!