Introduction
Trig identities are central to the IB Math syllabus, especially in Analysis and Approaches HL and SL. They allow students to simplify expressions, prove equations, and solve complex trigonometric problems. While the IB Math booklet includes key identities, exam success depends on knowing when and how to apply them quickly.
For many IB students, trigonometry can feel like a maze of formulas. But with practice, trig identities become powerful shortcuts that turn complicated problems into manageable steps.
Quick Start Checklist
- Memorize the most common trig identities.
- Practice using them in both algebraic and geometric problems.
- Apply them to simplify complex expressions.
- Understand when to use trig identities vs the calculator.
- Use RevisionDojo strategies to master exam-style questions.
Key Trig Identities in IB Math
The IB Math booklet provides the most important trig identities:
- Pythagorean identities:
- sin²θ + cos²θ = 1
- 1 + tan²θ = sec²θ
- 1 + cot²θ = csc²θ
- Double-angle identities:
- sin(2θ) = 2sinθcosθ
- cos(2θ) = cos²θ – sin²θ = 2cos²θ – 1 = 1 – 2sin²θ
- Addition and subtraction formulas:
- sin(A ± B) = sinAcosB ± cosAsinB
- cos(A ± B) = cosAcosB ∓ sinAsinB
These appear in both HL and SL exams, though HL students use them in more advanced contexts like calculus and proofs.
