Cosine rule

Description

Quiz on Cosine rule, created by Tom Woollin on 04/10/2017.
Tom Woollin
Quiz by Tom Woollin, updated more than 1 year ago
Tom Woollin
Created by Tom Woollin over 6 years ago
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Resource summary

Question 1

Question
Please select any/all of the equations that represent the cosine rule.
Answer
  • a²=b² -c² + 2ab² cos(A)
  • b² =a² + c² - 2ac cos(B)
  • cos(C)=a² +b² -c² / 2ab
  • a² =b² + c² -2bc cos(A)

Question 2

Question
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)
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

Question 3

Question
Work out the size of angle B.
Answer
  • 50.7°
  • 50.824°
  • 33.6°

Question 4

Question
Work out the length of AB.
Answer
  • 6.2cm
  • 13.1cm
  • 6.8cm
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