\textstyle - Used to over-ride automatic style rules and force text (inline) style.
{ \textstyle ...}
\textstyle command is used to over-ride automatic style rules and force text (inline) style. It stays in force until the end of math mode or the braced group, or until another style is selected.
\frac ab + {\textstyle \frac cd + \frac ef} + \frac gh