Notes
Cosine Rule
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The Cosine rule, similar to the sine rule, is true for all triangles.
The Cosine rule states that, in any triangle abc,
This is rule is useful when:
You know all 3 sides.
You know 2 sides and the angle at which they meet.
Example:
We can find A using the cosine rule:
cosA = 10^2 + 6^2 - 7^2
2(10)(6)
cosA = 87
120
A = 43.53*
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- This note explains the cosine rule, how to use it and when it is useful.
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- rory.examtime
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