I frequently tried to draw a triangle commutative diagram similar to the definition of projective modules for this question.

A module associated to an endomorphism of a vector bundle

so I searched in latex stackexchange and I find some relevant post.

then I copy paste the corresponding commands and I observed that that does not work for MO.

I copied the commands in this post:

https://tex.stackexchange.com/questions/191462/creating-triangle-commutative-diagram-with-tikz-cd

(I prefer $\gamma$ lies on a Dots arrows.

can I ask you to kindly help me to draw this diagram. such a diagram can present my meaning more precisely.

thank you in advance for your help.

P.S.: Even when I try a simple command as $$\begin{CD} A \\ @VVV \\ B \end{CD}$$

It does not work at MO.

`\require{AMScd}`

. See the post below. $\endgroup$ – Martin Sleziak Jan 16 '19 at 11:50