[sdiy] Divider or op-amp ?

[Ryan Williams]

for a voltage divider. R1 and R2. R1 is connected to the voltage source 
at one end, and connected to R2 at the other end. R2 connects to ground 
as well. the voltage where R1 and R2 connect is Vo. so 
Vo=Vin*R2/(R1+R2). so yea, thats what you said.

>>Given R1 and R2, where R1 is the "top" resistor, Vout = Vin * (R1+R2)/R2
> Are you sure ?
> My maths are really poor, but the following seems to make more sense :
> 
> Vout = Vin / (R1+R2)/R2
> 
> For instance, by using 2 Rs of 50K each, then Vin is divided by 2...
> 
> Am I missing something ?