Here are some examples of how to use "tenacious" in a sentence:
* She was a tenacious negotiator, refusing to settle for anything less than she deserved.
* The team's tenacious spirit led them to victory against all odds.
* He has a tenacious grip on his principles, even when faced with opposition.
You can also use words like persistent, determined, resolute, unwavering as synonyms for tenacious.