1. The problem statement, all variables and given/known data The coupoing coefficient of K' of a linear transformer is adjusted so that Zab is purely reissitive when ω= 25k rad/s. What is Zab? 2. Relevant equations Not sure 3. The attempt at a solution I'm not sure how to being this problem. For one, from what I've been reading I'm not sure how the connection between frequency and Zab is made. Also, I'm not sure what the question is asking for by 'purely resistive'. Does this mean there is no comblex part? I'm pretty sure I understand the coupling coefficient. I'm not sure how to apply it to this problem.