There are many times where one will need to use the square root symbol on a phone.
These next few steps can be taken to using the sign on an Android phone
• First, open the phone's keyboard
• Then, open the numeric keyboard to show all the numbers.
• Hold down and long press the number 2
• Doing so will load a popup with other options
• From that popup the square root symbol will be shown
To find it on an iPhone,
• Open Settings
• Find the keyboard tab
• Then, click Text Replacement
• Click the + symbol to add the square root, so that it can show on the keyboard.