This is also an example of a function of a function of a function, and we need to apply chain rule 3 times.

This can be written `y = sec^2u` where `u = 2x`.

If we let `v = sec u` then `y=v^2`.

So we have:

`y=v^2=sec^2 u`



`=(2v)(sec u tan u)(2)`

`=(4v)(sec u tan u)`

`=(4 sec u)(sec u tan u)`

`=4 sec^2 u tan u`

`=4 sec^2 2x tan 2x`