Blackman's impedance formula (Open loop gain)

[Electro_vass]

Homework Statement

Determine the input resistance using blackmans impedance formula.
I know all the ressisor values, and transistor data.

Homework Equations

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Blackmans impedance formula

The Attempt at a Solution

Our teacher has given us a example on how to find the open loop gain, but I don't understand what he has done. Do anyone know how he has found the open loop gain?

 

[milesyoung]

Do anyone know how he has found the open loop gain?

What is it, specifically, you're not sure about?

Note that the circuit shown is just a current divider.