Description

Resource Description

This Trigonometry: The Cosine Rule lesson pack is a high-quality, exam-focused digital maths resource designed for KS3 and GCSE (Foundation & Higher) students learning how to solve non-right-angled triangles using the Cosine Rule (Law of Cosines).

The resource carefully explains when and why the Cosine Rule is used, helping students move confidently beyond right-angled trigonometry. Through clear diagrams, structured explanations, and step-by-step worked examples, students learn how to calculate unknown sides and unknown angles, including questions that require inverse cosine and accurate rounding.

This pack is ideal for classroom teaching, revision, homework, intervention, and exam preparation, supporting students with both method clarity and exam technique.

📚 What’s Included

• Clear explanation of the Cosine Rule

• Formula presented clearly:

  • c² = a² + b² − 2ab cos(C)

• Identification of sides and angles in any triangle

• When to use the Cosine Rule:

  • Two sides and the included angle

  • All three sides to find an angle

• Step-by-step worked examples

• Use of inverse cosine (cos⁻¹)

• Practice questions worksheet

• Exam-style assessment questions

• Rounding answers to decimal places

• Clean, GCSE-aligned diagrams throughout

🎯 Ideal For

• KS3 extension and progression

• GCSE Foundation & Higher trigonometry

• Homework and independent learning

• Catch-up and intervention sessions

• Exam preparation and confidence building

This resource strengthens algebraic manipulation, trigonometric understanding, and calculator accuracy, ensuring students can confidently apply the Cosine Rule under exam conditions.

✨ Key Learning Outcomes

By the end of this lesson, students will be able to:

• State the Cosine Rule correctly

• Identify appropriate sides and angles

• Decide when the Cosine Rule is required

• Rearrange and apply the formula accurately

• Use inverse cosine to calculate angles

• Present clear, exam-ready solutions