Year 10 · Edexcel International GCSE Maths A (4MA1) Student Book 1 · Unit 1 Shape and Space 1 · p.71–72
Today you will
discover how to construct an angle bisector 作角平分线
find mistakes in other people's constructions 找错
explain why it works 说明原理
mark an exam question like an examiner 当考官
Success criteria成功标准
Arcs cross both arms
Two meeting arcs have equal radius
All arcs stay visible
Line goes from the vertex through the meeting point
Both halves measure the same
Tap ▶ to begin · ✎ pen · 🔤 words · ⛶ full screen
① Fold it 折一折
Fold your paper angle so the crease splits it exactly in half. Do the two halves match?
② Guess it 猜一猜
One volunteer drags the red line; class thumbs ↑ too high ↓ too low 👍 right. Then tap Check.
Round 1/4 Error: –° Total: 0°
Exam rule: no folding — ruler and compasses only. 考试不能折纸
Tap a card to flip it. Say the word aloud. Tap 🔊 to hear it. 点击翻牌,大声读出来
1Open your envelope: put the 5 picture cards in order and match the captions.
2Build it on Angle 1 (acute).
3Does it still work on Angle 2 (obtuse)?
4Measure both halves with a protractor: ____° and ____°
Stuck? 1 ask your team → 2 hint card −1 ★ → 3 ask a consultant team 卡住了:先问组员 → 提示卡(扣 1 颗星)→ 问顾问组
Team roles角色
Compass Captain — says centre & radius aloud
Ruler Referee — lines; keeps all arcs visible
Reporter — records, speaks for the team
Swap roles at each station.
Finished early? Become consultants: help by asking questions only. Or try a level‑up card ★
Reporter:
Show your construction under the camera. Say the steps.
Everyone else — whiteboards
AGREE
DISAGREE
ADD … and one sentence why
Check against the book (Ex 7 Q1) — tap Reveal:
Compass width for the second meeting arc: ×1.00
smallerwider
∠ABR = – ∠RBC = –
At each poster (P, Q, R, S):
1Measure the two halves.
2Is the blue line the bisector? Yes / No
3If no: what went wrong? use: arc · radius · vertex · centre
Write answers on your team record sheet. 答案写在小组记录表上,不要写在海报上。
Gallery route · when the timer rings, move to the next poster
PQRS
Round 1 of 4 · 2 minutes each
Do not measure first — read the arcs first, then check with the protractor.
Tap a statement → the diagram lights up. 点击右侧条目,图中对应线段高亮
1BP = BQ same radius, centre B
2PR = QR same radius, centres P and Q
3BR is common shared by both triangles
∴△BPR ≅ △BQR (SSS) so ∠PBR = ∠QBR 所以两角相等
On your booklet page A4
Work alone, exam conditions
Ruler and compasses only
Show all construction lines
Edexcel International GCSE Mathematics A · November 2024 · Paper 1H · Question 2
Next: swap and mark it with the official mark scheme.
Write on your partner's page: B2 / B1 / 0 and one comment — "To get full marks you should …"
Official wording: B2 for a fully correct angle bisector with all arcs shown. B1 for all arcs and no bisector drawn, or for a correct bisector within/on the guidelines but no arcs or insufficient arcs.
