The phrase "is convinced" is commonly used to express certainty or persuasion about something. However, if you want to add variety and depth to your writing, there are many synonyms that you can use to convey the same meaning. Some of these synonyms include " firmly believes," "is certain," "is persuaded," "is assured," "is confident," "has no doubt," "is fully convinced," "is resolute," "is satisfied," and "is determined." These words can help you to vary your language and create a stronger impact on your audience. So, the next time you find yourself relying too much on the phrase "is convinced," try incorporating one of these synonyms instead.