Sine and cosine rules (Higher)

What you'll learn

1. 1

   Imagine a triangle that isn't right-angled — like a slice of pizza that's been squished. The sine rule helps us find missing sides or angles in any triangle!

2. 2

   Let's explore a triangle. Drag the vertices to make different shapes — notice the sides and angles change.

3. 3

   Let's find side b using the sine rule.

4. 4

   In the sine rule, what does a/sin(A) equal?

5. 5

   Now meet the cosine rule. It's for when you know two sides and the angle between them, or all three sides.

6. 6

   Find side a using the cosine rule.

7. 7

   Which rule do you use if you know two sides and the angle between them?

8. 8

   In the cosine rule a² = b² + c² – 2bc cos(A), what does cos(A) mean?