RoyalSchrubber said:

Maybe they finally found out they got chain rule wrong.. I was actually amazed nobody pointed that out in the comments.. seems most viewers watched it for the show...

 

∂(f ° g)(t)=∂f(g(t)) ° ∂g(t) should be written as ∂(f °g)(t)=∂f(g(t)) ∂g(t).. where ° is composition operator and * multiplication...

Maybe the third show will be errata show!  When they were writing it out did they say times or composed with?