In the attachment is one page that I extract from the book "Differential Equations, Dynamical Systems, and an Introduction to Chaos". The two equations are highlighted.
I think the second one is incorrect, and I insert a question right below it. I inspect two different editions of the book and it is the same. It seems to be just a simple chain rule, and this drives me crazy.
Could you help explain why the second highlighted equation is written as it is?
Thanks much!