This video is all about using the cosine rule, and is aimed at around grade 6 GCSE Maths.
It’s quite likely to be a non calculator question. You need to find x after being given three sides of a triangle (x+2), (root73) and (2x-3); as well as one angle of 60 degrees.
Top Tips!
- Always write the formula
- Work methodically down the page
- Label angles as capitals, sides as lower case
- Make sure you use the inclusive angle – you need sides each side of your angle
- Don’t be tempted to plug all the information into your calculator – it’s better to calculate a little at a time
These types of questions appear in all the main examination boards, including Edexcel, AQA and OCR. They are popular and, once you have the basic principles, fairly similar. Please do stop the video, try the question and compare your solution.
If you would like to find out more try these
Cosine Rule; how to work out a length or angle in a triangle
Here’s a GCSE paper June 2018 with an example (Q17)
Please do leave a comment below if you are not sure. Alternately you can view my YouTube channel and leave a comment there – I’ll always try to respond as quickly as possible.
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