PlanetPhysics/Commutative Triangle Diagram

A commutative triangle diagram , $T_{CD}$, which is represented geometrically as: Failed to parse (unknown function "\begin{xy}"): {\displaystyle \begin{xy} *!C\xybox{ \xymatrix{ {A}\ar[rr]^{f}\ar[dr]_{h}&&{B}\ar[dl]^{g}\\ &{C}& } }\end{xy}} is also defined algebraically by the equality $h=g\circ f$