Two curves are tangent internally at a point if they lie on the same side of their common tangent at
Tangent Internally
See also
Tangent ExternallyExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Tangent Internally." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/TangentInternally.html