So, I'm asked to demonstrate the formulas for finding out the voltage labeled here as ΔU, which I'm given in my project document: I think I would be able to make the demonstrations without any outside help, if only I knew how I'm supposed to interpret this circuit branch in the middle. Is it connected in parallel to the branches with the resistors? Not only the two points seem to be disconnected, but even if they were connected, since that branch has no resistive elements on it, I would be inclined to believe no current flows through it, which obviously contradicts the assignment. What kind of circuit part is an interrupted conductive wire connected in parallel to two branches with resistors on them? I've attempted to collapse the resistors into series, then parallel equivalent resistances, but couldn't find a way to include the required branch into the new configurations. Also tried to apply Kirchhoff's laws, but there are 6 currents involved and couldn't find any way to simplify them out of the resulting equations. The whole thing just has me very confused. The formula to be proven for this circuit is: ΔU=U/4 *ΔR/R * 1/(1+0.5*(ΔR/R)).