A direct proof is a proof method by applying established facts, such as axioms and existing lemmas and theorems without further assumptions. 1
Logic
In logic, a direct proof means applying 2
- premise
- an instance of an axiom schemas
- an rule of inference
Here is an example, given modus ponens, and three promise
(premise) (premise) (premise) (modus ponens: 1, 2) (modus ponens: 2, 3) (modus ponens: 4, 5)