Theorems about conjoin and conjoin2.
Theorem:
(defthm pseudo-termp-of-conjoin (implies (pseudo-term-listp terms) (pseudo-termp (conjoin terms))))
Theorem:
(defthm pseudo-termp-of-conjoin2 (implies (and (pseudo-termp term1) (pseudo-termp term2)) (pseudo-termp (conjoin2 term1 term2))))