Formal:
* Demonstrate: "The experiment demonstrated the theory's validity."
* Establish: "The lawyer established the client's innocence."
* Verify: "The results were verified by an independent laboratory."
* Validate: "The study validated the effectiveness of the new medication."
* Confirm: "The eyewitness testimony confirmed the suspect's presence at the scene."
Informal:
* Show: "I'll show you how it's done."
* Exhibit: "The painting exhibits the artist's unique style."
* Illustrate: "This example illustrates the concept."
* Back up: "I need some evidence to back up my claims."
Other options:
* Substantiate: "They substantiated their accusations with concrete evidence."
* Justify: "The judge justified her decision with legal precedents."
It's important to choose the most appropriate synonym based on the specific meaning and context of your sentence.