Free IB Maths AA SL lesson: Cosine rule

A ready-to-teach IB Maths AA SL lesson on Cosine rule (Unit 3 · Geometry & Trigonometry): editable slides and teacher notes, free; a printable worksheet in 3 levels with answers for school plans. About 55 minutes.

IB Maths AA SL lesson slides on Cosine rule: title slide, learning objectives, a worked example and the exit ticket — Preview of the Cosine rule slides (IB Maths AA SL).

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What's inside

Slides (PowerPoint, editable) · freeabout 12 slides: do now, objectives, key ideas, a worked example step by step, “your turn”, practice QR code, exit ticket
Teacher notes (PDF) · freelesson plan with timings, common mistakes, homework links
Worksheet (PDF) · school plans5 questions, 20 marks: Fluency, Reasoning, Exam-style. Included with school plans and the teacher trial.
Answers (PDF) · school plansthe answer to every worksheet question, from its mark scheme. Included with school plans and the teacher trial.

Learning objectives

The cosine rule

Key vocabulary

cosine rule: a² = b² + c² − 2bccos A.
included angle: The angle between two known sides.
obtuse: Between 90° and 180°.

Common mistakes this lesson tackles

Working out b² + c² − 2bc first and then multiplying by cos A.
Using a non-included angle in the cosine rule for a side.
Forgetting the square root at the end.

Lesson plan

0–5 min	Do now: students write down what they remember about Sine rule and Angles of elevation & depression
5–8 min	Share the learning objective and success criteria
8–20 min	Teach: the worked example, step by step; students copy the method
20–25 min	Your turn: 1 mini-whiteboard question; check every board before moving on
25–42 min	Practise: the worksheet (5 questions in 3 levels, with school plans and the teacher trial) or the topic's practice questions online; move up a level after two right in a row
42–47 min	Plenary: 1-question exit ticket; collect it to plan the next lesson

For students: practise this topic

The worksheet's QR code opens the IB Maths AA SL Unit 3: Non right angled trigonometry practice questions.

What schools get

Set this lesson as homework, marked by AI against the mark scheme, with every result in your markbook (school Pro plan).
This lesson's worksheet in three levels, with its answers, ready to print.
Support, Core and Stretch versions and A/B copies of the worksheet from the full question bank, in the worksheet builder.
Create lesson: this lesson rebuilt for your class's next scheme-of-work lesson, from the full bank.

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Questions teachers ask

Is this lesson free?

The slides and the teacher notes are free to download with a free IB Math Revision teacher account (sign in with Google, Microsoft or email); no card. The printable worksheet in three levels and its answers are included with school plans and the free 30-day teacher trial.

Can I edit the slides?

Yes. The slides are an ordinary PowerPoint file: change, add or delete anything. They also open in Google Slides and Keynote. The logo and web address sit on the slide master, so your edits do not move them.

What do students use for homework?

The practice slide's QR code and web address take students to the IB Maths AA SL Unit 3: Non right angled trigonometry practice questions on ibmathrevision.com, where the free questions are open and the full bank comes with a plan.