Hello, dadon!
2) Find when
We have: .
From the defintion of , we have: .
Multiply the left fraction by
. .
. .
. .
. .
. .
. .
Therefore: .
The first line where y' appears is using the product rule on the previous line (the expression for y). Where the is one term and is the other term. Then you need to know that and .
Similarly where y'' appears this is the derivative of y', the first term is the derivative of the first term in y', and the remaining terms come from applying the product rule to the second term in the expression for y'.
RonL