4 Functions And Mappings

Discrete Structure · Unit 4

Functions and Mappings

Exam-focused notes for Functions and Mappings (Discrete Structure, BIT152): what the TU syllabus asks and how it has actually been tested, with 7 solved past questions from this unit.

What this unit covers

  • Function definition and notation
  • One-to-one and onto functions
  • Identity function
  • One-to-one correspondence
  • Boolean functions
  • Exponential functions
  • Ceiling and floor functions
  • Function plotting

Boolean functions

20825 marks

Define Boolean and exponential function. Discuss about partial ordering. [2+3]

--- A Boolean function is a function of the form: $$f: \{0, 1\}^n \rightarrow \{0, 1\}$$ It takes $n$ binary inputs (each either 0 or 1) and produces a single binary output (0 or 1). Boolean functions are expressed using Boolean operations: AND, OR, and NOT...

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208110 marks

Define Boolean function, exponential function and partial ordering. List the computer representations for following set over universal set $U = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}$: (a) Set that contains even number (b) Set that contains multiple of 5 (c) Set that contains number greater than 7 (d) Set that contains prime number. [6+4]

--- - Universal set: $U = \{0, 1, 2, 3, 4, 5, 6, 7, 8, 9\}$ (10 elements) - Required definitions: Boolean function, exponential function, partial ordering. - Sets to represent as bit strings over $U$: - (a) even numbers - (b) multiples of 5 - (c) numbers gr...

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Ceiling and floor functions

20805 marks

State ceiling function and floor function with examples. How mathematical induction can be used to prove the correctness of recursive algorithm? Illustrate with an example.[5]

--- Definition: The floor function of a real number $x$, denoted $\lfloor x \rfloor$, is the greatest integer less than or equal to $x$. $$\lfloor x \rfloor = \max\{n \in \mathbb{Z} \mid n \leq x\}$$ Examples: - $\lfloor 4.7 \rfloor = 4$ - $\lfloor 3 \rfloo...

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05 marks

Define celling and floor function. Explain Boolean function with example. [5]

--- The floor function of a real number x, denoted ⌊x⌋, is defined as the greatest integer less than or equal to x. $$\lfloor x \rfloor = \text{largest integer } n \text{ such that } n \leq x$$ Examples: - ⌊3.7⌋ = 3 - ⌊5⌋ = 5 - ⌊-2.3⌋ = -3 --- The ceiling f...

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One-to-one and onto functions

20805 marks

Explain one-to-one and onto function with example. What is identity function? [5]

A function f: A → B is called one-to-one (injective) if every element of the domain maps to a distinct element in the codomain. Formal Definition: f is one-to-one if f(x₁) = f(x₂) implies x₁ = x₂, for all x₁, x₂ ∈ A. In other words, no two different inputs ...

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One-to-one correspondence

20795 marks

Explain one-to-one correspondence with example. What is identity function? [5]

A function f: A → B is called a one-to-one correspondence (also called a bijection) if it is both one-to-one (injective) and onto (surjective). That means: - Injective: Every distinct element in A maps to a distinct element in B. - Formally: if f(x₁) = f(x₂...

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Function plotting

2080.15 marks

How do you plot graph for function $f(x) = x + 1$? Define ceiling, floor and exponential function. [5]

- Function to plot: $f(x) = x + 1$ - Terms to define: ceiling function, floor function, exponential function --- This is a linear function of the form $f(x) = mx + c$ with slope $m = 1$ and y-intercept $c = 1$. Steps to plot: 1. Identify the form. Since it ...

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