Homeschool Guide: These lesson plans are a guide for parents. Content may contain errors — always cross-reference with official exam board specifications.

G21: Exact Trig Values

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4 detailed 50-minute lessons with teaching scripts, worked examples, parent guides, and assessment criteria.

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Lesson Overview

Total Lessons: 4
Tier: Foundation and Higher
Duration: 50 minutes per lesson (200 minutes total)
Exam Boards: AQA, Edexcel, OCR, Eduqas, CCEA

Learning Objectives

Prerequisites

Materials & Equipment

Lesson 1: Introduction: Exact Trig Values

Duration: 50 minutes

Starter Activity (5 minutes)

Quick Recall

3 quick questions to activate prior knowledge about exact trig values. Use mini-whiteboard or paper.

Main Content (35 minutes)

Parent/Teacher Guide:
Before lesson: Read script below. Prepare materials. Pre-teach key vocab: G21.
If stuck: See Troubleshooting below. Break into smaller steps.
Extension: See Stretch & Challenge section.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: Exact Trig Values. Goal: by the end you can write down the exact value of cos 30°, using the method shown step by step. Connects to trigonometry ratios (R12/G) because you'll reuse its method throughout today's work."
Mins 5-15 - Direct Instruction: 1) Define: "Exact Trig Values is..." 2) Key principle: "Most important:..." 3) Draw diagram, label live. 4) Real example: "Like Write down the exact value of cos 30° - a real example worked through in full..."
Mins 15-25 - Guided Practice: Ex1: Teacher models. Ex2: Student tries with guidance. Ex3: Student independent.
Mins 25-35 - Independent Practice: 3-5 questions. Immediate feedback.
Worked Example 1: Basic

Q: Write down the exact value of cos 30°

  1. What is asked? Write
  2. Recall knowledge:
  3. Apply: From the table: cos 30° = √3/2. Where it comes from: half an equilateral triangle of side 2 gives sides 1, 2, √3 — cos 30° = adjacent/hypotenuse = √3/2.
  4. Check: Check the units named in the question and sense-check the size of your answer.
  5. Answer: √3/2

Tip: "Show working - method marks > answer marks."

Worked Example 2: Multi-step

Q: Write down the exact value of tan 30°

  1. Break down: Separate parts?
  2. Solve each: Same half-equilateral triangle: tan 30° = opposite/adjacent = 1/√3. Rationalised: 1/√3 = √3/3 (multiply top and bottom by √3).
  3. Combine: The parts chain: each answer feeds the next step of the question.
  4. Final answer: B1 for 1/√3 or √3/3 — both forms are accepted. 0.577 is not.
Worked Example 3: Data/Application

Q: A right-angled triangle has a 30° angle and a hypotenuse of 10 cm. Write down the exact length of the side opposite the 30° angle.

  1. Read data: Axes, units, scale
  2. Patterns: Trends, anomalies
  3. Explain: Why? Using exact trig values
  4. Conclude: Evidence-based

Common Questions & Troubleshooting

Q: "Why does work this way?"
A: Analogy: "Write down the exact value of cos 30°". Try re-draw or re-write the worked example from memory, then check it against the model answer.
Q: "Wrong answers on calculations."
A: Checklist: units? formula? calculator mode? sig figs?
Q: "Can't remember key terms."
A: Flashcards (term front, def+diagram back). Spaced repetition: day 1, 3, 7.
Q: "Exam wording confuses me."
A: Commands: Describe=what you see; Explain=reasons; Evaluate=pros/cons+judgement; Calculate=working+units.
Q: "Running out of time."
A: 1 mark/min. Skip hard, return. Attempt all - partial marks count.

Assessment & Model Answers

Mastery Checklist:
  • [ ] Define Exact Trig Values in own words
  • [ ] Identify features in diagram
  • [ ] Explain process step-by-step
  • [ ] Apply to unfamiliar context
  • [ ] Score 80%+ on past paper question

Model Answer: Past Paper Question

Q: Write down the exact value of cos 30°

  • 1 mark: [Key terminology]
  • 1 mark: [Mechanism/process]
  • 1 mark: [Application/example]
  • 1 mark: [Evaluation - Higher]

Model response: "[Complete answer with expected detail/terminology]"

Why full marks: [What makes this strong]

Stretch & Challenge (Grade 8-9):
  • Synoptic links: Connect to G20-pythagoras-trigonometry / G22-sine-cosine-rules
  • Real-world: Research use in industry, medicine or research
  • Advanced calc: Try a more challenging variant
  • Critical: "Evaluate limitations of today's model"
  • Research: Recent discovery on exact trig values, summarise 100 words

Plenary (5 mins)

Label the Diagram

Unlabelled diagram - write all parts in 1 min

Assessment Criteria

Lesson 2: Core Concepts: Exact Trig Values

Duration: 50 minutes

Starter Activity (5 minutes)

Review Previous Lesson

Quick recap: write 3 key points from last lesson on exact trig values. Use mini-whiteboard or paper.

Main Content (35 minutes)

Parent/Teacher Guide:
Before lesson: Read script below. Prepare materials. Pre-teach key vocab: G21.
If stuck: See Troubleshooting below. Break into smaller steps.
Extension: See Stretch & Challenge section.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: Exact Trig Values. Goal: by the end you can write down the exact value of cos 30°, using the method shown step by step. Connects to trigonometry ratios (R12/G) because you'll reuse its method throughout today's work."
Mins 5-15 - Direct Instruction: 1) Define: "Exact Trig Values is..." 2) Key principle: "Most important:..." 3) Draw diagram, label live. 4) Real example: "Like Write down the exact value of cos 30° - a real example worked through in full..."
Mins 15-25 - Guided Practice: Ex1: Teacher models. Ex2: Student tries with guidance. Ex3: Student independent.
Mins 25-35 - Independent Practice: 3-5 questions. Immediate feedback.
Worked Example 1: Basic

Q: Write down the exact value of cos 30°

  1. What is asked? Write
  2. Recall knowledge:
  3. Apply: From the table: cos 30° = √3/2. Where it comes from: half an equilateral triangle of side 2 gives sides 1, 2, √3 — cos 30° = adjacent/hypotenuse = √3/2.
  4. Check: Check the units named in the question and sense-check the size of your answer.
  5. Answer: √3/2

Tip: "Show working - method marks > answer marks."

Worked Example 2: Multi-step

Q: Write down the exact value of tan 30°

  1. Break down: Separate parts?
  2. Solve each: Same half-equilateral triangle: tan 30° = opposite/adjacent = 1/√3. Rationalised: 1/√3 = √3/3 (multiply top and bottom by √3).
  3. Combine: The parts chain: each answer feeds the next step of the question.
  4. Final answer: B1 for 1/√3 or √3/3 — both forms are accepted. 0.577 is not.
Worked Example 3: Data/Application

Q: A right-angled triangle has a 30° angle and a hypotenuse of 10 cm. Write down the exact length of the side opposite the 30° angle.

  1. Read data: Axes, units, scale
  2. Patterns: Trends, anomalies
  3. Explain: Why? Using exact trig values
  4. Conclude: Evidence-based

Common Questions & Troubleshooting

Q: "Why does work this way?"
A: Analogy: "Write down the exact value of cos 30°". Try re-draw or re-write the worked example from memory, then check it against the model answer.
Q: "Wrong answers on calculations."
A: Checklist: units? formula? calculator mode? sig figs?
Q: "Can't remember key terms."
A: Flashcards (term front, def+diagram back). Spaced repetition: day 1, 3, 7.
Q: "Exam wording confuses me."
A: Commands: Describe=what you see; Explain=reasons; Evaluate=pros/cons+judgement; Calculate=working+units.
Q: "Running out of time."
A: 1 mark/min. Skip hard, return. Attempt all - partial marks count.

Assessment & Model Answers

Mastery Checklist:
  • [ ] Define Exact Trig Values in own words
  • [ ] Identify features in diagram
  • [ ] Explain process step-by-step
  • [ ] Apply to unfamiliar context
  • [ ] Score 80%+ on past paper question

Model Answer: Past Paper Question

Q: Write down the exact value of cos 30°

  • 1 mark: [Key terminology]
  • 1 mark: [Mechanism/process]
  • 1 mark: [Application/example]
  • 1 mark: [Evaluation - Higher]

Model response: "[Complete answer with expected detail/terminology]"

Why full marks: [What makes this strong]

Stretch & Challenge (Grade 8-9):
  • Synoptic links: Connect to G20-pythagoras-trigonometry / G22-sine-cosine-rules
  • Real-world: Research use in industry, medicine or research
  • Advanced calc: Try a more challenging variant
  • Critical: "Evaluate limitations of today's model"
  • Research: Recent discovery on exact trig values, summarise 100 words

Plenary (5 mins)

Label the Diagram

Unlabelled diagram - write all parts in 1 min

Assessment Criteria

Lesson 3: Application: Exact Trig Values

Duration: 50 minutes

Starter Activity (5 minutes)

Review Previous Lesson

Quick recap: write 3 key points from last lesson on exact trig values. Use mini-whiteboard or paper.

Main Content (35 minutes)

Parent/Teacher Guide:
Before lesson: Read script below. Prepare materials. Pre-teach key vocab: G21.
If stuck: See Troubleshooting below. Break into smaller steps.
Extension: See Stretch & Challenge section.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: Exact Trig Values. Goal: by the end you can write down the exact value of cos 30°, using the method shown step by step. Connects to trigonometry ratios (R12/G) because you'll reuse its method throughout today's work."
Mins 5-15 - Direct Instruction: 1) Define: "Exact Trig Values is..." 2) Key principle: "Most important:..." 3) Draw diagram, label live. 4) Real example: "Like Write down the exact value of cos 30° - a real example worked through in full..."
Mins 15-25 - Guided Practice: Ex1: Teacher models. Ex2: Student tries with guidance. Ex3: Student independent.
Mins 25-35 - Independent Practice: 3-5 questions. Immediate feedback.
Worked Example 1: Basic

Q: Write down the exact value of cos 30°

  1. What is asked? Write
  2. Recall knowledge:
  3. Apply: From the table: cos 30° = √3/2. Where it comes from: half an equilateral triangle of side 2 gives sides 1, 2, √3 — cos 30° = adjacent/hypotenuse = √3/2.
  4. Check: Check the units named in the question and sense-check the size of your answer.
  5. Answer: √3/2

Tip: "Show working - method marks > answer marks."

Worked Example 2: Multi-step

Q: Write down the exact value of tan 30°

  1. Break down: Separate parts?
  2. Solve each: Same half-equilateral triangle: tan 30° = opposite/adjacent = 1/√3. Rationalised: 1/√3 = √3/3 (multiply top and bottom by √3).
  3. Combine: The parts chain: each answer feeds the next step of the question.
  4. Final answer: B1 for 1/√3 or √3/3 — both forms are accepted. 0.577 is not.
Worked Example 3: Data/Application

Q: A right-angled triangle has a 30° angle and a hypotenuse of 10 cm. Write down the exact length of the side opposite the 30° angle.

  1. Read data: Axes, units, scale
  2. Patterns: Trends, anomalies
  3. Explain: Why? Using exact trig values
  4. Conclude: Evidence-based

Common Questions & Troubleshooting

Q: "Why does work this way?"
A: Analogy: "Write down the exact value of cos 30°". Try re-draw or re-write the worked example from memory, then check it against the model answer.
Q: "Wrong answers on calculations."
A: Checklist: units? formula? calculator mode? sig figs?
Q: "Can't remember key terms."
A: Flashcards (term front, def+diagram back). Spaced repetition: day 1, 3, 7.
Q: "Exam wording confuses me."
A: Commands: Describe=what you see; Explain=reasons; Evaluate=pros/cons+judgement; Calculate=working+units.
Q: "Running out of time."
A: 1 mark/min. Skip hard, return. Attempt all - partial marks count.

Assessment & Model Answers

Mastery Checklist:
  • [ ] Define Exact Trig Values in own words
  • [ ] Identify features in diagram
  • [ ] Explain process step-by-step
  • [ ] Apply to unfamiliar context
  • [ ] Score 80%+ on past paper question

Model Answer: Past Paper Question

Q: Write down the exact value of cos 30°

  • 1 mark: [Key terminology]
  • 1 mark: [Mechanism/process]
  • 1 mark: [Application/example]
  • 1 mark: [Evaluation - Higher]

Model response: "[Complete answer with expected detail/terminology]"

Why full marks: [What makes this strong]

Stretch & Challenge (Grade 8-9):
  • Synoptic links: Connect to G20-pythagoras-trigonometry / G22-sine-cosine-rules
  • Real-world: Research use in industry, medicine or research
  • Advanced calc: Try a more challenging variant
  • Critical: "Evaluate limitations of today's model"
  • Research: Recent discovery on exact trig values, summarise 100 words

Plenary (5 mins)

Exam Question Speed Round

5 quick questions, 1 min each. Mark together.

Assessment Criteria

Lesson 4: Exam Practice: Exact Trig Values

Duration: 50 minutes

Starter Activity (5 minutes)

Review Previous Lesson

Quick recap: write 3 key points from last lesson on exact trig values. Use mini-whiteboard or paper.

Main Content (35 minutes)

Parent/Teacher Guide:
Before lesson: Read script below. Prepare materials. Pre-teach key vocab: G21.
If stuck: See Troubleshooting below. Break into smaller steps.
Extension: See Stretch & Challenge section.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: Exact Trig Values. Goal: by the end you can write down the exact value of cos 30°, using the method shown step by step. Connects to trigonometry ratios (R12/G) because you'll reuse its method throughout today's work."
Mins 5-15 - Direct Instruction: 1) Define: "Exact Trig Values is..." 2) Key principle: "Most important:..." 3) Draw diagram, label live. 4) Real example: "Like Write down the exact value of cos 30° - a real example worked through in full..."
Mins 15-25 - Guided Practice: Ex1: Teacher models. Ex2: Student tries with guidance. Ex3: Student independent.
Mins 25-35 - Independent Practice: 3-5 questions. Immediate feedback.
Worked Example 1: Basic

Q: Write down the exact value of cos 30°

  1. What is asked? Write
  2. Recall knowledge:
  3. Apply: From the table: cos 30° = √3/2. Where it comes from: half an equilateral triangle of side 2 gives sides 1, 2, √3 — cos 30° = adjacent/hypotenuse = √3/2.
  4. Check: Check the units named in the question and sense-check the size of your answer.
  5. Answer: √3/2

Tip: "Show working - method marks > answer marks."

Worked Example 2: Multi-step

Q: Write down the exact value of tan 30°

  1. Break down: Separate parts?
  2. Solve each: Same half-equilateral triangle: tan 30° = opposite/adjacent = 1/√3. Rationalised: 1/√3 = √3/3 (multiply top and bottom by √3).
  3. Combine: The parts chain: each answer feeds the next step of the question.
  4. Final answer: B1 for 1/√3 or √3/3 — both forms are accepted. 0.577 is not.
Worked Example 3: Data/Application

Q: A right-angled triangle has a 30° angle and a hypotenuse of 10 cm. Write down the exact length of the side opposite the 30° angle.

  1. Read data: Axes, units, scale
  2. Patterns: Trends, anomalies
  3. Explain: Why? Using exact trig values
  4. Conclude: Evidence-based

Common Questions & Troubleshooting

Q: "Why does work this way?"
A: Analogy: "Write down the exact value of cos 30°". Try re-draw or re-write the worked example from memory, then check it against the model answer.
Q: "Wrong answers on calculations."
A: Checklist: units? formula? calculator mode? sig figs?
Q: "Can't remember key terms."
A: Flashcards (term front, def+diagram back). Spaced repetition: day 1, 3, 7.
Q: "Exam wording confuses me."
A: Commands: Describe=what you see; Explain=reasons; Evaluate=pros/cons+judgement; Calculate=working+units.
Q: "Running out of time."
A: 1 mark/min. Skip hard, return. Attempt all - partial marks count.

Assessment & Model Answers

Mastery Checklist:
  • [ ] Define Exact Trig Values in own words
  • [ ] Identify features in diagram
  • [ ] Explain process step-by-step
  • [ ] Apply to unfamiliar context
  • [ ] Score 80%+ on past paper question

Model Answer: Past Paper Question

Q: Write down the exact value of cos 30°

  • 1 mark: [Key terminology]
  • 1 mark: [Mechanism/process]
  • 1 mark: [Application/example]
  • 1 mark: [Evaluation - Higher]

Model response: "[Complete answer with expected detail/terminology]"

Why full marks: [What makes this strong]

Stretch & Challenge (Grade 8-9):
  • Synoptic links: Connect to G20-pythagoras-trigonometry / G22-sine-cosine-rules
  • Real-world: Research use in industry, medicine or research
  • Advanced calc: Try a more challenging variant
  • Critical: "Evaluate limitations of today's model"
  • Research: Recent discovery on exact trig values, summarise 100 words

Plenary (5 mins)

Exam Question Speed Round

5 quick questions, 1 min each. Mark together.

Assessment Criteria

📝 Mark Scheme Guidance

How examiners mark G21: Read the command word carefully — State = one word/phrase (1 mark), Describe = pattern or detail (2 marks), Explain = reason with "because" (2–3 marks), Compare = similarities AND differences, Evaluate = both sides + conclusion. Method marks are awarded for correct working even if the final answer is wrong. Always show your working — unexplained answers score zero for AO2.

Success on G21 questions: Underline the command word, count the marks (one mark per point expected), and answer in the format the command word demands.

Board Notes & Revision Links

This lesson is examined by: AQA 8300 | Edexcel 1MA1 | OCR J560 | Eduqas C300 | CCEA M-units. Tier and paper details vary - always check your board's current specification.

Follow-up revision: G21-exact-trig-values on GCSE Revise (notes, flashcards and auto-graded target tests for this exact topic).

📐 Reference Diagram

x y y = x² Origin (0,0)

✏️ Draw-Along Instructions

Parent/teacher: Draw the shape using a ruler. Label all sides with their lengths. Mark equal angles with arcs. Add any parallel-line arrows. Write the formula you will use inside the shape.

Display the reference diagram (or draw it live) while pupils copy. Check each label as it is added.

Homework & Consolidation

Recommended Resources

🎓 Smart Lesson (Guided)