Is this an application of the chain rule?

Aug 2019
5
0
Italy
Hello, please see the attached image, the author of the book says it is the application of the chain rule, but it seems different to me.

If it was a chain rule thing then there would be z-squared on the "outside" and (tk -ok) on the "inside", and z = tk-ok.

Or have I misunderstood some ways of using the chain rule?Is-this-a-chain-rule.gif
 

romsek

Math Team
Sep 2015
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1,608
USA
This is a perfect example of the chain rule.
 
Aug 2019
5
0
Italy
It may be that I did not consider the original function; does the chain rule work in this case? Can it be used in this case, because o is a function of w?

Is-this-a-chain-rule-1.gif

TIA!
 
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romsek

Math Team
Sep 2015
2,875
1,608
USA
It can always be used. If $o_k$ is not a function of $w_{jk}$ then $\dfrac{\partial}{\partial w_{jk}}o_k = 0$
 
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