Analysis of linked contours

[tipa]

Let's try to derive the amplitude-frequency characteristic for two inductively coupled circuits with a coupling coefficient varying from 0.1 to 1 through 0.1.
The curves turn out to be angular, regardless of the increase in the number of counts from 128,000 to 128,000,000. The question to experts, why is this !? How to make the charts more pleasant and real?