Constructing a triangle given two angles and the side length between them
I can construct a triangle given two angles and the side length between them.
Constructing a triangle given two angles and the side length between them
I can construct a triangle given two angles and the side length between them.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- The side can be drawn accurately with a ruler
- Both angles should be accurately measured with a protractor
- Where the lines marking each angle intersect is where the lines should be drawn to
- All triangles with the same measurements are congruent
Keywords
Congruent - If one shape can fit exactly on top of another using rotation, reflection or translation, then the shapes are congruent.
Common misconception
Pupils may struggle to spot congruent triangles if they only look for ASA (angle-side-angle).
Encourage pupils to add any further information to diagrams, like the third angle, before starting to prove congruence.
To help you plan your year 11 maths lesson on: Constructing a triangle given two angles and the side length between them, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 11 maths lesson on: Constructing a triangle given two angles and the side length between them, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 maths lessons from the Loci and construction unit, dive into the full secondary maths curriculum, or learn more about lesson planning.
Equipment
Pair of compasses, protractor and ruler
Licence
Starter quiz
6 Questions






Step 1 -
Use a ruler to draw side AC of 7 cm.
Step 2 -
Use a protractor to measure 52° at A and mark a faint point.
Step 3 -
Draw a ray line through A to show direction of AB.
Step 4 -
Set compasses to width of 9 cm and mark an arc on the ray.
Step 5 -
Label point where arc meets the ray as B.
Step 6 -
Use a ruler to connect C and B.
Exit quiz
6 Questions





