On density of truth of the intuitionistic logic in one variable

Intuitionistic logic is an important subsystem of the classical one. In intuitionistic logic the effective interpretation and mechanical extraction of programs from proofs are allowed. The programming interpretation of intuitionistic propositional logic by simply typed lambda-calculus is a significant part of interest of computer scientists. The intuitionistic natural deductions are actually the same as simply λ terms (Curry-Howard isomorphism). For any set of formulas A ⊂ F we define its density, denoted by μ(A), as follows: