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# Automatic theorem provers

### Zenon

Zenon is an automatic theorem that handles first-order logic with equality. Its most important feature is that it outputs the proofs of the theorems, in Coq-checkable form.

- License: BSD like
- Web site: http://focal.inria.fr/zenon/

### MetiTarski

MetiTarski is an automatic theorem prover based on a combination of resolution and a decision procedure for the theory of real closed fields. It is designed to prove theorems involving *real-valued special functions* such as log, exp, sin, cos and sqrt. In particular, it is designed to prove *universally quantified inequalities* involving such functions. This problem is undecidable, so MetiTarski is necessarily incomplete. Nevertheless, MetiTarski is remarkably powerful.

- License: MIT

### E Theorem Prover

E is a theorem prover for full first-order logic with equality. It accepts a problem specification, typically consisting of a number of first-order clauses or formulas, and a conjecture, again either in clausal or full first-order form. The system will then try to find a formal proof for the conjecture, assuming the axioms.

If a proof is found, the system can provide a detailed list of proof steps that can be individually verified. If the conjecture is existential (i.e. it’s of the form “there exists an X with property P”), the latest versions can also provide possible answers (values for X).

- License: GNU GPL

### SPASS

SPASS is an automated theorem prover for first-order logic with equality.

- License: BSD
- Web site: http://www.spass-prover.org/