Rohit I am grateful for the information.
This procedure I am familiar with and should apply whenever I want to insert a math input cell. I would like to know if there is a way to permanently change how it works in Stylesheet defaut.
In that case, you should edit your question to make it clear that you want to know how to change the default style.
This can be done in several ways, check this workflow doc for details.
From the Format menu select Style / Input (Cmd - 9 on a Mac).
