use bootstrap 4 in angular 9 code example
Example 1: install bootstrap in angular 9
npm install bootstrap --save
Example 2: installing bootstrap in angular 9
.... "styles": [ "node_modules/bootstrap/dist/css/bootstrap.min.css", "src/styles.css" ], "scripts": [ "node_modules/jquery/dist/jquery.min.js", "node_modules/bootstrap/dist/js/bootstrap.min.js" ].....