Without referring to Theorem 5.3.8, prove part (b) of Corollary 5.3.9: If A andB are countable sets, then is countable.

Richard Vollberg Computer Science Notes Week 1 *All formulas must start with an equal sign 1. Basic Formulas + (Addition), - (Subtraction), / (Division), * (Multiplication), ^ (Exponent/Power) Basic Functions: 1. Sum Function =Sum(FirstCell:LastCell) -The cells in the parentheses is called the range of cells ex. =Sum(A1:A5), A1=1, A2=2, A3=3, A4=4, A5=5 Answer: 15 *Excel will automatically know the appropriate answer if the formula is correctly written 2. Average Function =Average(FirstCell#:LastCell#) 3. Max & Minimum Function =Max(FirstCell#:LastCell#) =Min(FirstCell#:LastCell#) 4. Count Functions =Count(FirstCell#:LastCell#) =CountA(FirstCell#:LastCell#) *Count function is for numeric data and Count