CISC 102 Lecture Notes - Lecture 3: Null Set, Empty Set, Complex Instruction Set Computing
12 Sep 2018
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Homework of the week is to be taken up thursday. Let a and b be two sets, where every element of a is also an element of b. For example: a = {red, black}, b = {red, black, green} Observe that: if a a then a b. We can say that a is contained in b, or a is a subset of b. Let x and y be two sets such that a x implies a y, which also means that a y implies a x. We can then also say x y and y x. Thus, the sets are equal, so we can write x = y. If x = y then x y and y x. These two sentences can be expressed in a single sentence as: X = y if and only if x y and y x. Let x and y be two sets such that:
