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

G6: Geometric Proof

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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: Geometric Proof

Duration: 50 minutes

Starter Activity (5 minutes)

Quick Recall

3 quick questions to activate prior knowledge about geometric proof. Use mini-whiteboard or paper.

Main Content (35 minutes)

Parent/Teacher Guide:
Before lesson: Read script below. Prepare materials. Pre-teach key vocab: G6.
If stuck: See Troubleshooting below. Break into smaller steps.
Extension: See Stretch & Challenge section.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: Geometric Proof. Goal: by the end you can prove that the base angles of an isosceles triangle are equal, using the method shown step by step. Connects to congruence criteria (G5) because you'll reuse its method throughout today's work."
Mins 5-15 - Direct Instruction: 1) Define: "Geometric Proof is..." 2) Key principle: "Most important:..." 3) Draw diagram, label live. 4) Real example: "Like Prove that the base angles of an isosceles triangle are equal. - 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: Prove that the base angles of an isosceles triangle are equal.

  1. What is asked? Prove
  2. Recall knowledge: Congruence criteria: SSS, SAS, ASA, RHS (AAS counts as ASA); Proof structure: claim → given → facts → reasons → ∎ (or QED)
  3. Apply: Draw the angle bisector from the apex. The two triangles share: the bisected angle (construction), two equal sides (definition of isosceles), and the common base line. By SAS the triangles are congruent → corresponding angles equal → base angles equal ∎
  4. Check: Check the units named in the question and sense-check the size of your answer.
  5. Answer: State the complete final answer.

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

Worked Example 2: Multi-step

Q: Prove that the base angles of an isosceles triangle are equal.

  1. Break down: Separate parts?
  2. Solve each: Draw the angle bisector from the apex. The two triangles share: the bisected angle (construction), two equal sides (definition of isosceles), and the common base line. By SAS the triangles are congruent → corresponding angles equal → base angles equal ∎
  3. Combine: The parts chain: each answer feeds the next step of the question.
  4. Final answer: M1 for a valid construction, A1 for the congruence, A1 for the conclusion. Naming the criterion (SAS) is the reason mark.
Worked Example 3: Data/Application

Q: Prove that the base angles of an isosceles triangle are equal.

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

Common Questions & Troubleshooting

Q: "Why does Congruence criteria: SSS, SAS, ASA, RHS (AAS counts as ASA) work this way?"
A: Analogy: "Prove that the base angles of an isosceles triangle are equal.". 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 Geometric Proof 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: Prove that the base angles of an isosceles triangle are equal.

  • 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 G5-congruence-criteria / G7-transformations
  • 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 geometric proof, summarise 100 words

Plenary (5 mins)

Label the Diagram

Unlabelled diagram - write all parts in 1 min

Assessment Criteria

Lesson 2: Core Concepts: Geometric Proof

Duration: 50 minutes

Starter Activity (5 minutes)

Review Previous Lesson

Quick recap: write 3 key points from last lesson on geometric proof. Use mini-whiteboard or paper.

Main Content (35 minutes)

Parent/Teacher Guide:
Before lesson: Read script below. Prepare materials. Pre-teach key vocab: G6.
If stuck: See Troubleshooting below. Break into smaller steps.
Extension: See Stretch & Challenge section.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: Geometric Proof. Goal: by the end you can prove that the base angles of an isosceles triangle are equal, using the method shown step by step. Connects to congruence criteria (G5) because you'll reuse its method throughout today's work."
Mins 5-15 - Direct Instruction: 1) Define: "Geometric Proof is..." 2) Key principle: "Most important:..." 3) Draw diagram, label live. 4) Real example: "Like Prove that the base angles of an isosceles triangle are equal. - 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: Prove that the base angles of an isosceles triangle are equal.

  1. What is asked? Prove
  2. Recall knowledge: Congruence criteria: SSS, SAS, ASA, RHS (AAS counts as ASA); Proof structure: claim → given → facts → reasons → ∎ (or QED)
  3. Apply: Draw the angle bisector from the apex. The two triangles share: the bisected angle (construction), two equal sides (definition of isosceles), and the common base line. By SAS the triangles are congruent → corresponding angles equal → base angles equal ∎
  4. Check: Check the units named in the question and sense-check the size of your answer.
  5. Answer: State the complete final answer.

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

Worked Example 2: Multi-step

Q: Prove that the base angles of an isosceles triangle are equal.

  1. Break down: Separate parts?
  2. Solve each: Draw the angle bisector from the apex. The two triangles share: the bisected angle (construction), two equal sides (definition of isosceles), and the common base line. By SAS the triangles are congruent → corresponding angles equal → base angles equal ∎
  3. Combine: The parts chain: each answer feeds the next step of the question.
  4. Final answer: M1 for a valid construction, A1 for the congruence, A1 for the conclusion. Naming the criterion (SAS) is the reason mark.
Worked Example 3: Data/Application

Q: Prove that the base angles of an isosceles triangle are equal.

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

Common Questions & Troubleshooting

Q: "Why does Congruence criteria: SSS, SAS, ASA, RHS (AAS counts as ASA) work this way?"
A: Analogy: "Prove that the base angles of an isosceles triangle are equal.". 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 Geometric Proof 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: Prove that the base angles of an isosceles triangle are equal.

  • 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 G5-congruence-criteria / G7-transformations
  • 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 geometric proof, summarise 100 words

Plenary (5 mins)

Label the Diagram

Unlabelled diagram - write all parts in 1 min

Assessment Criteria

Lesson 3: Application: Geometric Proof

Duration: 50 minutes

Starter Activity (5 minutes)

Review Previous Lesson

Quick recap: write 3 key points from last lesson on geometric proof. Use mini-whiteboard or paper.

Main Content (35 minutes)

Parent/Teacher Guide:
Before lesson: Read script below. Prepare materials. Pre-teach key vocab: G6.
If stuck: See Troubleshooting below. Break into smaller steps.
Extension: See Stretch & Challenge section.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: Geometric Proof. Goal: by the end you can prove that the base angles of an isosceles triangle are equal, using the method shown step by step. Connects to congruence criteria (G5) because you'll reuse its method throughout today's work."
Mins 5-15 - Direct Instruction: 1) Define: "Geometric Proof is..." 2) Key principle: "Most important:..." 3) Draw diagram, label live. 4) Real example: "Like Prove that the base angles of an isosceles triangle are equal. - 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: Prove that the base angles of an isosceles triangle are equal.

  1. What is asked? Prove
  2. Recall knowledge: Congruence criteria: SSS, SAS, ASA, RHS (AAS counts as ASA); Proof structure: claim → given → facts → reasons → ∎ (or QED)
  3. Apply: Draw the angle bisector from the apex. The two triangles share: the bisected angle (construction), two equal sides (definition of isosceles), and the common base line. By SAS the triangles are congruent → corresponding angles equal → base angles equal ∎
  4. Check: Check the units named in the question and sense-check the size of your answer.
  5. Answer: State the complete final answer.

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

Worked Example 2: Multi-step

Q: Prove that the base angles of an isosceles triangle are equal.

  1. Break down: Separate parts?
  2. Solve each: Draw the angle bisector from the apex. The two triangles share: the bisected angle (construction), two equal sides (definition of isosceles), and the common base line. By SAS the triangles are congruent → corresponding angles equal → base angles equal ∎
  3. Combine: The parts chain: each answer feeds the next step of the question.
  4. Final answer: M1 for a valid construction, A1 for the congruence, A1 for the conclusion. Naming the criterion (SAS) is the reason mark.
Worked Example 3: Data/Application

Q: Prove that the base angles of an isosceles triangle are equal.

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

Common Questions & Troubleshooting

Q: "Why does Congruence criteria: SSS, SAS, ASA, RHS (AAS counts as ASA) work this way?"
A: Analogy: "Prove that the base angles of an isosceles triangle are equal.". 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 Geometric Proof 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: Prove that the base angles of an isosceles triangle are equal.

  • 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 G5-congruence-criteria / G7-transformations
  • 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 geometric proof, summarise 100 words

Plenary (5 mins)

Exam Question Speed Round

5 quick questions, 1 min each. Mark together.

Assessment Criteria

Lesson 4: Exam Practice: Geometric Proof

Duration: 50 minutes

Starter Activity (5 minutes)

Review Previous Lesson

Quick recap: write 3 key points from last lesson on geometric proof. Use mini-whiteboard or paper.

Main Content (35 minutes)

Parent/Teacher Guide:
Before lesson: Read script below. Prepare materials. Pre-teach key vocab: G6.
If stuck: See Troubleshooting below. Break into smaller steps.
Extension: See Stretch & Challenge section.
Teaching Script (35 mins):
Mins 0-5 - Hook: "Today: Geometric Proof. Goal: by the end you can prove that the base angles of an isosceles triangle are equal, using the method shown step by step. Connects to congruence criteria (G5) because you'll reuse its method throughout today's work."
Mins 5-15 - Direct Instruction: 1) Define: "Geometric Proof is..." 2) Key principle: "Most important:..." 3) Draw diagram, label live. 4) Real example: "Like Prove that the base angles of an isosceles triangle are equal. - 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: Prove that the base angles of an isosceles triangle are equal.

  1. What is asked? Prove
  2. Recall knowledge: Congruence criteria: SSS, SAS, ASA, RHS (AAS counts as ASA); Proof structure: claim → given → facts → reasons → ∎ (or QED)
  3. Apply: Draw the angle bisector from the apex. The two triangles share: the bisected angle (construction), two equal sides (definition of isosceles), and the common base line. By SAS the triangles are congruent → corresponding angles equal → base angles equal ∎
  4. Check: Check the units named in the question and sense-check the size of your answer.
  5. Answer: State the complete final answer.

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

Worked Example 2: Multi-step

Q: Prove that the base angles of an isosceles triangle are equal.

  1. Break down: Separate parts?
  2. Solve each: Draw the angle bisector from the apex. The two triangles share: the bisected angle (construction), two equal sides (definition of isosceles), and the common base line. By SAS the triangles are congruent → corresponding angles equal → base angles equal ∎
  3. Combine: The parts chain: each answer feeds the next step of the question.
  4. Final answer: M1 for a valid construction, A1 for the congruence, A1 for the conclusion. Naming the criterion (SAS) is the reason mark.
Worked Example 3: Data/Application

Q: Prove that the base angles of an isosceles triangle are equal.

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

Common Questions & Troubleshooting

Q: "Why does Congruence criteria: SSS, SAS, ASA, RHS (AAS counts as ASA) work this way?"
A: Analogy: "Prove that the base angles of an isosceles triangle are equal.". 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 Geometric Proof 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: Prove that the base angles of an isosceles triangle are equal.

  • 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 G5-congruence-criteria / G7-transformations
  • 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 geometric proof, 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 G6: 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 G6 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: G6-geometric-proof 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)