I will refer to the following two screenshots :
as you can see, the definition of dz has gone from being (a-y) to a(1-a) which is pointed out in the reading titled Clarification of “dz”. Now, although it’s right in mentioning that
dL/dz in code as dz is (a-y) and da/dz will be a(1-a), I think there is a mistake here.
This is because although the definition of dz is changed whereas dw and db are still xi*dz.
Hope I am making sense.
@IshanDave Check this:
Hi,
Thank you for the clarification, I understand there was a confusion with the definition of dz. However, as @IshanDave mentions, I also think that in this slide, it should be written dz= a - y
Thanks,
I agree with this. The clarification only mentions where a(1-a) came from, not whether dz = a(1-a) is the correct use. I also think that dz = (a-y) is what it should be and the clarification should mention that.
@theghks2 agreed, however at this point students should know which dz Andrew is referring to.
@IshanDave Thanks for pointing this out, I also had the same doubt. As others have also pointed out the correct implementation should be dz = (a-y). However the clarification provided just after the video is also wrong and makes it more confusing. The clarification says-
“dz” as a shorthand to refer to da/dz=a(1−a).
To clarify, earlier in this week’s videos, Andrew used the name “dz” to refer to a different derivative: dL/dz=a−y
Rather, the clarification should have mentioned that the specific line is a typo. Also: dz=da/dz=a(1−a) was never introduced in lectures.
