In Google Docs click on the Add-ons tab in the menu bar and select Get Add-ons. Open your document in Google Docs and put your cursor where you want to put a symbol. The equations and maths symbols you type will appear in the placeholder.
Before you can use any of the symbols make sure you have selected New Equation.
Click the Insert menuSpecial Characters. A simple shortcut is to draw the symbol into the box below the search bar. Docs has a dedicated way to add mathematical equations so you dont have to use the special characters menu. When done creating your math or science text click the Insert Math button to add it to your Google Doc or Form.