Propositional and predicate logic
A proposition has a fixed truth value. p → q is false only when p is true and q is false; it is vacuously true when p is false. Predicate logic quantifies over a domain: ∀x P(x) fails if any element violates P; ∃x P(x) succeeds if any element satisfies P.
Check yourself: Have you checked the implication when the antecedent is false?
Combinatorics and recurrences
C(n, k) = n!/(k!(n−k)!) counts selections without order. Recurrences define sequences through prior terms. Solve by finding a closed-form solution that satisfies both the recurrence and initial conditions. The Master Theorem applies to specific divide-and-conquer forms.
Check yourself: Does your base case produce the correct initial value?
Calculus: limits, continuity, and integration
A function is continuous at a point when its limit equals its value. A definite integral computes net signed area. Integration by parts and substitution require matching differentials. Verify convergence before evaluating an improper integral.
Check yourself: Is the integrand defined and continuous on the interval, including endpoints?
Graph theory fundamentals
A simple graph with n vertices and m edges satisfies the handshaking lemma: the degree sum equals 2m. A tree on n vertices has exactly n − 1 edges. An Euler circuit exists when every vertex has even degree and the graph is connected. Distinguish paths, walks, and circuits.
Check yourself: Are you counting edges or vertices, and is the graph connected?
Probability for CS
For equally likely outcomes, probability is favorable/total. Use conditional probability P(A|B) = P(A ∩ B)/P(B) and distinguish independence from mutual exclusivity. Expected value is linear: E(X + Y) = E(X) + E(Y) regardless of dependence.
Check yourself: Are the outcomes truly equally likely under your counting?