1. The problem statement, all variables and given/known data I was able to find the solution to this problem but I don't understand where it comes from. A series RL circuit is connect to a 110-V ac source. If the voltage across the resistor is 85 V, find voltage across inductor. 2. Relevant equations Not sure. 3. The attempt at a solution Solution is given as V_s^2 = V_r^2 + V_l^2 then solve for V_l, I don't understand were that equation comes from or how it applies here. We are currently starting to learn how to solve circuits with the phasor method.