In the standard ellipse of variable axes dimensions $( a, b, c= \sqrt{a^2-b^2}), $
what is the geometrical significance of triangle inequality difference for variable $(2a-2c)$ in the first and third cases?
The second case result is known.. in the ongoing question in-circle diameter.
It was ensured to be geometrically constructible and answer interesting... hope forms my part of problem solving attempt.