We covered input and output impedances for an opamp and i understand the maths of it and also i can see that the formula appears to behave properly but i take issue on some things.

A pdf containing the formula and info i am referring to can be found at: zebu.uoregon.edu/~rayfrey/431/notes9.pdf

The main problem that i am having is with the formaul for input impedance: Zin = R1(1+BAol)

where R1 is the input resistance of the opamp itself

So if Rin and Rf(which is the feedback resistor) are equal, B will be 1.

Then by this formula, Zin will be R1(1+Aol).

In a normal inverting amplifier, following the "golden rules" the input current is (Vin - 0)/Rin

Zin is then Vin/(Vin/Rin) = Rin

So i dont understand how this generalised formula for input impedance can apply to an inverting amplifier?