MATH145 Lecture 12: MATH 145 Lecture 12
13 Dec 2017
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S f (cid:15) h and s g (cid:15) h s (f g) (cid:15) h. In words, from f we can conclude f g. In words, from f g and f we can conclude g. In words, to prove f g we suppose f then prove g, and we suppose g and prove f. V26. (f g) (f g) ( f g) S (cid:15) t = t. in words, we can always conclude that t = t is true under any assumptions. From s = t we can conclude t = s. From r = s and s = t we can conclude r = t. If s (cid:15) s = t then (s (cid:15) [f ]x 7 t s (cid:15) [f ]x 7 s ). In words, if (cid:15) s = t, we can always replace any occurrence of the term s by the term t.
