Using a unit circle can help develop a deeper understanding of working with right-angled triangles.
In this lesson, students explore the behaviour of a radius vector as it rotates around a unit circle.
The coordinates of the end of the radius are (cos θ, sin θ), where θ is the anticlockwise angle from the positive x-axis.
This provides a way to introduce students to the sine and cosine ratios as functions of an angle, and avoids the need to memorise SOHCAHTOA and procedures that may be poorly understood.
Download contents Zip file including:
- 1 x PDF of full lesson plan
- 1 x PDF of trigonometry worksheet for main activity
Why teach this?
Trigonometry in right-angled triangles gives students an appreciation of the power of mathematics to precisely calculate lengths that would be tedious to draw and measure.
Key curriculum links
- Use mathematical language and properties precisely
- Use trigonometric ratios in similar triangles to solve problems involving right-angled triangles
