**Circuit Gain**

Suppose I have Vin = V1 + V2*sin(wt) and Vout = V3 + V4*sin(wt). How do I calculate gain? I know it's Vout/Vin, but my lab handout tells me it's a constant (the lab handouts are garbage, though, so it could be wrong). I have zero background in circuits, I'd already spent 40+ hours on this lab before I even got to the circuit gain part, it took me hours to figure out what the "Z" in my handout stood for and I've spent even more hours running in circles around Google trying to figure out how to calculate it, I just need to finish this lab report. Please help.