Get them exploring this important method for solving triangles, says Colin Foster…
In this maths lesson, students will explore how the sine rule allows possible triangles to be solved, given combinations of two angles and a side or two sides and an angle that is not in between.
They are asked to invent angles and side lengths that will lead to (i) a unique solution, (ii) two possible solutions (the ‘ambiguous case’), and (iii) no solutions (no such triangle).
Experimenting with different values helps students to see when each particular scenario will arise.
Why teach this?
The sine rule is a powerful way to capture the relationships between the side lengths and angles in a triangle.
Key curriculum links
- Know and apply the sine rule
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Angles of Triangles – KS4 Maths Lesson Plan
