my answer is this

(Ro.Rl/Ri)/(RoCos+RlCos)+(RoRlCis)/(RoCos+RlCos)

 

Like pulling teeth .... hopefully I got it right.

 

Like I said about the teeth ...

Error in the last line - missing sign.

 

If you have the answer what help do you need?

 

i dont know if it is the right answer or not.

 

I don't think it's right. Your answer doesn't even include β .

T_N_K has it right; I get the same result he does..

 

cheers guys

 

Like the Electrician, my answer agrees with the one from TNK. Your original answer is incorrect.

hgmjr