Answer:
(command) windows + period
Explanation:
win + period will bring up a menu of emojis and symbols, you should then have a top bar with multiple options, you go to symbols (circled in red in attached screenshots).
Then, your menu should look similar to the third screenshot provided:
Then, scroll through the options until you get to math symbols, (fourth screenshot) click it, and scroll until you find your symbol :)
If you can't find it in math symbols, just look through other groups until you find it.