Given two closed curves, the circuminscribed curve is simultaneously inscribed in the outer one and circumscribed on the inner one.
Circuminscribed
See also
Circumscribed, Inscribed, Poncelet's Porism, Steiner ChainExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Circuminscribed." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Circuminscribed.html