
Everything you need to teach solving trigonometric equations to senior maths and pre-calculus students. Use the worked examples, identity reference sheets, practice questions and lesson plans to move students from solving simple sin x = k problems, to finding general solutions, to applying trigonometric identities under exam conditions.
Curriculum-aligned coverage of solving trigonometric equations, mapped to the Australian Maths Curriculum v9.0 (Mathematical Methods Units 1-4 and Specialist Mathematics) and to the US Algebra 2, Precalculus and AP Precalculus standards (Learning Objective 3.10.A: solve equations and inequalities involving trigonometric functions). The sequence starts with simple equations of the form sin x = k, moves through factoring and quadratic-in-trig equations, and finishes with identity-driven equations and general solutions in radians.
.png)

Worked examples that show students how to find every solution, not just the first one. The pack walks through the reference-angle method, reading second solutions off the unit circle, restricting answers to a given interval such as 0 ≤ x ≤ 2π, and writing general solutions in the form x = nπ + (-1)^n α or x = 2nπ ± α. The decision step — "do I need every solution, the solutions in this interval, or the general form?" — gets its own walkthrough.
Differentiated questions across three levels. Foundation questions stay with single-step equations like 2 cos x = 1 over a stated interval. Standard questions introduce factoring, quadratic-in-trig forms such as 2 sin²x - sin x - 1 = 0, and equations that need a Pythagorean identity to reduce. Extension questions push into general solutions, equations involving compound angles, and modelling problems that produce a trig equation from a real context.

Real-world applications that make the equations feel useful, not abstract. Tasks include finding the times of day when tide height equals a target value, calculating the angles at which a Ferris wheel passenger sits at a given height, and modelling the displacement of a simple harmonic oscillator. Each application starts with the equation already in context, so students see why solving for x actually matters.
Step-by-step solutions for every question, written the way you would model the working on the board. Students see the original equation, the rearrangement, the reference angle, the quadrant analysis, the full set of solutions in the required interval and the final answer with units (degrees or radians). Useful for self-correction and for setting as homework.
Common-error callouts drawn from real classroom marking. Losing the second solution by only using the calculator's principal value, mixing up degrees and radians, dropping solutions when dividing through by a trig term, and forgetting to write the general solution when asked for all solutions all get explicit walkthroughs so students stop repeating them.
- You in approximately four minutes
Introducing trigonometric equations and the unit circle
The opening lessons start with simple trigonometric equations of the form sin x = k, cos x = k and tan x = k. Worked examples build the reference-angle method from the unit circle, so students stop relying on the calculator to give them only one answer. Visual walkthroughs show how to read the second solution off the unit circle for sine and cosine, and how to use the period of tan x to find every solution in a stated interval. By the end of the introduction, students can solve any single-trig-function equation over a domain like 0 ≤ x ≤ 2π and write their solutions clearly in either degrees or radians.
Identity-driven equations and harder exam-style problems
The middle lessons move into general solutions and applied problems where the equation comes from a real context. Students learn to write x = nπ + (-1)^n α for sine equations and x = 2nπ ± α for cosine equations, and to switch between specific-interval and general-solution forms depending on what the question asks. Applied tasks include tide height, Ferris-wheel position, average daily temperature and simple harmonic motion. Each problem starts with a sentence of context, gives students the model equation, and asks them to solve it — the same shape as senior exam questions across VCE, HSC, AP Precalculus and A-level.
General solutions, intervals and applied periodic problems
The extension lessons handle the equations students find hardest: quadratic-in-trig equations such as 2 sin²x + sin x - 1 = 0 that need factoring, equations that need a Pythagorean identity (sin²x + cos²x = 1) or double-angle formula to reduce to a single trig function, and equations involving compound angles like sin(2x + π/3) = 0.5. The pack walks through the choose-an-identity decision, the substitution, the back-substitution and the interval check. Harder problems combine several of these techniques in a single question, mirroring senior exam style.