Tricky limits questions, bit of help please

[priscared]

So here i am, trying to understand a lossless transmission line that has open-circuit termination. So i start with the generic Zi, the equivalent impedance seen by the source, then allow the load impedance (Zl) to approach infinity. As you can see, i have no idea how to do it. It's been way to long since I've done complex limits. Please see attached workings. This is a math quesiton, you obviously don't need to know electronics to answer it.
Cheers

 

[daudaudaudau]

Just divide the nominator and denominator by ZL.

 

[priscared]

that makes life easy!
cheers