In Google Docs both square root and cube root can be inserted with the help of Equation tool. The ‘√’ is the radical symbol that represents the square root symbol in Google Docs.
There are two ways to insert square root in Google Docs, either by using \sqrt LaTeX shortcuts or Google Docs Equation.
How to type square root in Google Docs
Open Google Docs on your desktop computer
Put the cursor where you want to type the square root
In the “Menu bar” click on “Insert” option then navigate and click on “Equation”

Now type \sqrt and press the space bar from the keyboard, see below screenshot for reference-

As the square root symbol appears in Google Docs type the number under the square root.

How to type square root in Google Docs with equation toolbar
Open your Google Docs document
Navigate to the “Menu bar” and go to “Insert” -> click on “Equation”. If equation toolbar is not visible, then under the “View” click and enable the “show equation toolbar”
Now under the New equation toolbar, choose “Math Operations”

Select the square root symbol from the list

As the square root symbol appears you can enter the number. By following similar steps cube root can also be inserted in Google Docs.
You can also learn to write fractions and degree symbol and strikethrough in Google Docs.