# How to draw a commutative diagram with a half circle added on its left?

Here is the figure I wanna draw:

I know how to draw the commutative diagram without the extension on the left of my figure, here is the code:

\documentclass{book}
\usepackage{amsmath}
\usepackage{tikz-cd}
\usepackage{mathtools, amssymb}
\usepackage{pst-node, auto-pst-pdf}

\title{Zero & non-zero homomorphism figures}
\author{Marwa Mosallam }
\date{May 2021}

\begin{document}
$\begin{tikzcd}[sep=large] M \ar[r] \ar[d, "\mathrm{Pinch}" ' ] \arrow[dr, dashed, "\beta_1 + \beta_2 + \beta_3", sloped] & * \ar[d] \\ M \vee M \vee M \ar[r, "{(\beta_1 , \beta_2 , \beta_3)}" '] & N \arrow[r] & \dots \end{tikzcd}$
\end{document}


Any help on how to add this half circle in the figure?

EDIT:

I have a problem in the order of putting $E$ and $B$ to get 2 bended arrows as in my picture above.

Here is my new code:

$\begin{tikzcd}[sep=large] M \ar[r] \dar[bend right] % <--- \dar["\mathrm{Pinch}" ] & * \ar[d] & E \\ M \vee M \vee M \ar[r, "{(\beta_1, \beta_2, \beta_3)}" '] & N \\ \end{tikzcd}$


EDIT:

Another trial, here is my new code:

$\begin{tikzcd}[sep=large] M \ar[r] \dar[bend right] % <--- \dar["\mathrm{Pinch}" ] & * \ar[d]\\ S' \dar[bend right]\\ M \vee M \vee M \ar[r, "{(\beta_1, \beta_2, \beta_3)}" '] & N \\ \end{tikzcd}$


• Your MWE does not reproduce showed image
• if you like to bend some arrow, just add to its option bend right or bend left, for example, based on your MWE:
\documentclass{book}
\usepackage{tikz-cd}

\begin{document}
$\begin{tikzcd}[sep=large] M \ar[r] \dar["\mathrm{Pinch}" ] \ar[dr, dashed, "\beta_1 + \beta_2 + \beta_3", sloped] \dar[bend right] % <--- & * \ar[d] \\ M \vee M \vee M \ar[r, "{(\beta_1, \beta_2, \beta_3)}" '] & N \dar \\ & \dots \end{tikzcd}$
\end{document}


• But if I would like to bend 2 times as in my drawing .... how should I do this? Jul 18, 2021 at 2:46
• Sorry for the not accurate code .... I adjusted it for myself but I am keeping it the same in the question so that your answer will match what I am saying. Jul 18, 2021 at 2:54
• I need a bended arrow from A to E and then from E to B ... I always mistakes what should come after what. Jul 18, 2021 at 2:56
• I think I solved my problem ... thank you so much for your help. Jul 18, 2021 at 4:36
• I am so sorry that you saw me like this, I did not do this intentionally, I will correct my attitude in my later posts. I am sorry I just forgot to reaccept your answer, I accepted it now. at the very beginning I thought your answer will help me, but then when I tried I got stuck, this is why I erased my acceptance. Anyway I am very sorry if my behavior was not nice, I promise I will be thorough in accepting the answers and in asking questions. Jul 18, 2021 at 12:13