20. Trigonometry
iGCSE (2021 Edition)
20.05 Cosine rule (Extended)
Interactive practice questions
Which of the following is true for the given triangle?
$\cos\theta=\frac{b^2+a^2-c^2}{2bc}$cosθ=b2+a2−c22bc
A
$\cos\theta=\frac{b^2+c^2-a^2}{2bc}$cosθ=b2+c2−a22bc
B
$\cos\theta=\frac{b^2+c^2-a^2}{2ab}$cosθ=b2+c2−a22ab
C
$\cos\theta=\frac{a^2+c^2-b^2}{2bc}$cosθ=a2+c2−b22bc
D
Easy
< 1min
To use the cosine rule to find the length of $AC$AC, which angle would need to be given?
Easy
< 1min
Find the length of $a$a using the cosine rule.
Round your answer to two decimal places.
Medium
3min
Find the length of $a$a using the cosine rule.
Round your answer to two decimal places.
Medium
2min
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