Myths about teaching can hold you back
- Year 9
Congruent triangles (ASA and AAS)
I can appreciate and use the criteria by which triangles are congruent (ASA and AAS).
- Year 9
Congruent triangles (ASA and AAS)
I can appreciate and use the criteria by which triangles are congruent (ASA and AAS).
Lesson details
Key learning points
- By knowing two angles and a length in the triangle and image, you can prove congruence.
- The angle pairs must be identical.
- This rule is derived from the SAS criteria for congruence.
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.
Encourage pupils to add any further information to diagrams, like the third angle, before starting to prove congruence.
To help you plan your year 9 maths lesson on: Congruent triangles (ASA and AAS), download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 9 maths lesson on: Congruent triangles (ASA and AAS), 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 3 maths lessons from the Geometrical properties: similarity and Pythagoras' theorem unit, dive into the full secondary maths curriculum, or learn more about lesson planning.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which line segment has not been drawn to the same length as the other two?
Q2.The angle marked $$x°$$ is °.
Q3.The missing angle in triangle XYZ is °.
Q4.Triangle ABC is congruent to triangle XYZ, therefore YZ = cm.
Q5.Triangle ABC and triangle XYZ are congruent, therefore is 9.6 cm.
Q6.All __________ are similar.
Assessment exit quiz
6 Questions
Q1.The criteria ASA (angle-side-angle) and AAS (angle-angle-side) are equivalent. True or false?
Q2.Triangle ABC and triangle XYZ are congruent by AAS/ASA. Which angle in triangle XYZ is 46°?
Q3.Match each triangle on the top row to the triangle on the bottom row that it is congruent to.
a -
d
b -
f
c -
e
Q4.Which of the following triangles is not guaranteed to be congruent to the other three triangles?
Q5.Which of these quadrilaterals can be split into two congruent triangles using one diagonal?
Q6.Complete this congruence proof. ∠ABD = ∠BDC as they are given in the diagram, BD is a shared edge and ∠ADB = ∠DBC as they are equal angles, so triangle ABD and BDC are congruent by SAS.
