Constructing Angle Bisectors | I Do, We Do, You Do | Year 10 Maths | Print Free

Teach angle-bisector constructions with this print-free Year 10 maths lesson. The 83-slide editable PowerPoint combines animated demonstrations, illustrated vocabulary, matched modelling, assessment for learning and practice with worked answers.

Pupils use compasses and a straightedge to construct internal angle bisectors, calculate the resulting angles and explain why the method works using SSS congruence. External bisectors, perpendicular distance and a triangle’s incentre extend their understanding.

WHAT IS INCLUDED
• 83 editable PowerPoint slides with questions and answers.
• Six retrieval questions and six prerequisite questions, with grouped answers.
• Four vocabulary slides with diagrams and definitions.
• A 3 × 2 I Do–We Do grid with three matched pairs.
• Animated construction demonstrations and completed WE DO solutions.
• Teaching on constructing an external angle bisector.
• 20 AFL questions, each immediately followed by its answer.
• 12 minimally different practice questions in three blocks, with diagrams and answers.
• A compact whole-class page showing Developing, Secure, Greater Depth and a Super Challenge together.
• Worked construction, calculation and proof solutions, plus an exit check and answers.
• A branded TES thumbnail, three preview images and suggested listing copy.

MODELLING AND VOCABULARY
The matched examples move from constructing a bisector to calculating both resulting angles and explaining why they are equal. Diagrams support definitions of vertex, angle arms, angle bisector, arc, radius and intersection. Further vocabulary covers internal and external bisectors, perpendicular distance, the incentre, congruent triangles, SSS, SAS and RHS.

MINIMALLY DIFFERENT PRACTICE
One block varies the angle while retaining the construction method. Another fixes the angle and first-arc radius while varying the radius of the paired arcs, helping pupils notice what changes. The final block applies the same SSS justification to different angles.

DIFFERENTIATED PRACTICE
Developing consolidates constructions and half-angle calculations. Secure covers equal radii, an equation involving equal angles and an external bisector. Greater Depth develops a congruence proof and construction of a triangle’s incentre, including its equal-distance property.

The Super Challenge explores the angle where two internal bisectors meet. Pupils calculate an angle, derive a general formula and apply it to a different triangle. Worked solutions use angle sums and bisector properties.

PRINT-FREE CLASSROOM USE
Pupils draw constructions and show their working in exercise books. They need compasses, a straightedge, a measuring ruler, a protractor to set up given angles, and a pencil. Use PowerPoint Slide Show mode for the animations.

Suitable for Year 10 teaching, consolidation or revision. Pupils should know basic angle facts and simple linear equations. Select proof and generalisation tasks to match prior knowledge.