TrevTutor’s explanation of truth trees and natural deduction is far more intuitive than most blackboard lectures. Watch his video on "Negating Quantifiers" before attempting problem set 2 of 18.090.
That is the standard. Now go prove it. Keywords used: 18090 introduction to mathematical reasoning mit extra quality, MIT 18.090, mathematical reasoning, proof techniques, Velleman How to Prove It, MIT OpenCourseWare, mathematics study guide. Now go prove it
| Week | MIT Topic | Extra Quality Action | | :--- | :--- | :--- | | 1-2 | Propositional Logic, Truth Tables | Read Velleman Ch. 1-2. Do 10 truth-table problems without the table (use algebraic simplification). | | 3-4 | Quantifiers, Predicate Logic | Watch TrevTutor’s "Negating Quantifiers." Write the negation of every statement in your lecture notes. | | 5-6 | Direct & Contrapositive Proofs | Read Hammack Ch. 5. For each proof, write the contrapositive statement before starting. | | 7-8 | Proof by Contradiction & Induction | The "(\sqrt2) is irrational" proof is classic. Then attempt a double induction (induction on two variables). | | 9-10 | Set Theory, Russell’s Paradox | Watch VSauce’s "The Banach-Tarski Paradox" (not directly in 18.090, but builds intuition for weird sets). | | 11-12 | Relations & Functions (Injective/Surjective) | Prove that if ( f ) and ( g ) are injective, then ( g \circ f ) is injective. Do it three ways: direct, contrapositive, contradiction. | | 13-14 | Cardinality, Cantor’s Theorem | Read the "Hilbert’s Hotel" essay by George Gamow. Then attempt a proof that the power set of ( \mathbbN ) is uncountable. | Completing 18.090 with extra quality is not about getting an A. It is about acquiring a new mental operating system. You will start to see logical fallacies in political speeches. You will recognize when a news article uses a biased sample (an inductive fallacy). You will debug code more systematically, because you understand the difference between necessary and sufficient conditions. The questions no longer ask
Introduction: The Hidden Curriculum of Mathematical Maturity For most undergraduates, the transition from high school calculus to university-level proofs is a profound shock. You might have aced the AP Calculus BC exam, earned a 5, and even dabbled in some linear algebra. Yet, when you first encounter a course like 18.090: Introduction to Mathematical Reasoning at MIT, a strange thing happens. The numbers disappear. The equations become sparse. In their place appear cryptic symbols: ( \forall, \exists, \ni, \implies, \iff ). The questions no longer ask, “What is ( x )?” but rather, “Is this statement true for all integers?” earned a 5
The resources listed here—Velleman, Hammack, PRIMES problems, and the mental habits of refutation and definition recitation—transform 18.090 from a hurdle into a launchpad.
After you finish the course, write a one-page proof that mathematical reasoning is the most transferable skill in the university curriculum . Use quantifiers, induction, and at least one proof by contradiction.