11. For a formal proof of the powerset construction, please see the Powerset construction article. 12. A formal proof is written in a formal language instead of a natural language. 13. "' Proof theory "'is the study of formal proofs in various logical deduction systems. 14. In the 1960s formal proofs were presented under different assumptions by continuum of agents. 15. If so, I would like to see the formal proof . 16. Having a definition of formal proof makes the concept of proof amenable to study. 17. While no formal proof yet exists, numerical simulations offer supporting evidence of its validity. 18. The interactive applet conveys a good intuition of the idea behind the formal proof . 19. One example of such a formal proof is as follows. 20. Formal proofs often are constructed with the help of computers in interactive theorem proving.
