Please select any/all of the equations that represent the cosine rule.
a²=b² -c² + 2ab² cos(A)
b² =a² + c² - 2ac cos(B)
cos(C)=a² +b² -c² / 2ab
a² =b² + c² -2bc cos(A)
This is a worked example so you know what to do later on (if you didn't already know) Q:Find the length of BC. (Please select the correct working and answer)
We want the length a so we use the equation in the form: a² =b² +c² -2bc cos(A), so a² =7² +3² -2*7*3 * cos(35), a² =58 - 42 * cos(35) a² =23.595 (approximately)
a=4.86
a=6.42
Work out the size of angle B.
50.7°
50.824°
33.6°
Work out the length of AB.
6.2cm
13.1cm
6.8cm
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