# How can we set \displaystyle for a whole text?

Since there is no preamble to set \displaystyle for the whole text, how can we do to avoid writing \displaystyle each time we write a new formula?

(but I still want to write inline)

For example if I want to write this :

$$\sum\limits_{k=1}^{n} u_k$$ is ... so we have $$\sum\limits_{k=1}^{n} u_k ^2 = ...$$, and it implies that $$\sum ...$$. but I don't want to write \displaystyle each time.

• Ummm, use $$<content>$$ Dec 27 '20 at 15:53
• Yes but I want to write inline.
– math
Dec 27 '20 at 16:02
• This seems a bit unusual to me. What are actually the places where you need displaystyle? Do you need it for limits/integrals? Or do you want to have bigger fractions? Dec 27 '20 at 16:13
• Actually both : mostly when i use sums and integrals
– math
Dec 27 '20 at 16:14
• $\displaystyle{........................................................}$ Dec 27 '20 at 16:20
• But please, @math, do not use display style in titles! Dec 27 '20 at 16:21
• yes i know about that, thank you @amWhy, i edited my question to be clearer
– math
Dec 27 '20 at 16:23
• Thank you very much ! it's very useful.
– math
Dec 27 '20 at 17:43
• In my opinion, \displaystyle should be very seldomly used. If you want it to be big, make it appear in the center with $$...$$. Otherwise, you make paragraphs have too much spacing so they do not flow as easily as they should Dec 28 '20 at 2:17

1. There is not really a way to force display style math without invoking \displaystyle every time you enter "math mode" using a single dollar sign. There is probably some hackery which could be made to work (as Martin Sleziak suggests), but this is not really ideal.
2. You shouldn't do this, anyway. Display style mathematics really ought to be reserved for displayed equations and expressions. Putting display style mathematics inline monkeys with line spacing, and creates a rather inconsistently typeset document. $$\sum_{k=1}^{n} u_k$$ is correct. $$\sum\limits_{k=1}^{n} u_k$$ really isn't (note how it stretches the interline-spacing).