condition inside string is not working – angular

I want to show a different icon depending on the if my value is true or false

<span><i class="fas fa-caret-"+({{ extendedOptionsContainer ? "down" : "up" }})+"></i></span>

So if extendedOptionsContainer is true, icon will be down, and if its not it will be up, but this wont work because inside this string and "", any help?

>Solution :

  <span><i [ngClass]="'fas fa-caret-' + (extendedOptionsContainer ? 'down' : 'up')"></i></span>