The cosine rule
… is a favourite exam question and deals with calculating an angle or a length in any triangle. The questions tend to be on calculator exam papers as you’ll be working with fractions, squares and the cosine of an angle.
- Make sure you use the ‘inclusive angle’ ie. you’ll need two sides and the angle in the middle
- Always label accurately with capital letters for angles and small case for sides
- Don’t be tempted to plug all the information into your calculator – it’s better to calculate a little at a time
Here’s a picture of my notes that might help:
Watch videos on YouTube: