i am unable to understand how to get output impedance in a feedback circuit using a transistor

 

Divide output voltage by output current.

 

but after shorting the input side,i am unable to understand how Vi=Vf for current series and Vi=-Vf for voltage series (as given in bolystad)

 

What is "bolystad?"

 

Probably Boylestad, the author of circuit analysis text book widely used in foundation courses.