Triangle Interior -- from Wolfram MathWorld

The interior of the triangle is the set of all points inside a triangle, i.e., the set of all points in the convex hull of the triangle

How to Calculate the Sides and Angles of Triangles Using Pythagoras' Theorem, Sine and Cosine Rule - Owlcation

Spherical Excess

Morphogenesis Parametric House

What is the simplest-to-understand proof of the existence of the nine-points circle of a triangle? - Quora

CausalGraphEntanglementEntropyGeneralized

Altitude (triangle) - Wikiwand

A Triangle Median Meet

Arbitrary non-intersecting quadrilateral, can be very concave : r/desmos

CausalGraphEntanglementEntropyNaive

Circumscribed Circle

Pat'sBlog: Volume F- H