Introduction to Proofs

An introductory course designed to teach the fundamental concepts and techniques of mathematical proofs.

Advanced Topics

Mathematical Induction

The Power of Induction

Mathematical induction is a proof technique used to show that a statement holds for all natural numbers.

How It Works

  1. Base Case: Show the statement is true for the first value (usually \( n = 1 \)).
  2. Inductive Step: Assume the statement is true for \( n = k \), and use this to prove it is true for \( n = k + 1 \).

If both steps work, the statement is true for all natural numbers!

Why Induction Matters

Induction is like climbing a ladder: if you can get on the first step, and you can always go to the next step, you can climb forever.

Formula

\[ \text{If statement is true for } n = 1, \text{ and } \forall k, \text{ true for } n = k \Rightarrow \text{ true for } n = k+1, \text{ then true for all } n. \]

Key Formula

\[P(1) \wedge (P(k) \Rightarrow P(k+1)) \Rightarrow \forall n \in \mathbb{N}, P(n)\]

Examples

  • Proving that the sum of the first \( n \) natural numbers is \( \frac{n(n+1)}{2} \).

  • Showing that \( 2^n > n \) for all \( n \geq 1 \).

In a Nutshell

Induction proves statements are true for all natural numbers by climbing from one case to the next.

Key Terms

Induction
A proof method using a base case and an inductive step to prove statements for all natural numbers.