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cosine and sine rules? (1 Viewer)
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DownInFlames
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cosine rule:
A^2 = B^2 + C^2 - BCcosA
cosA = (B^2 + C^2- A^2)/BC
A^2 = B^2 + C^2 - BCcosA
cosA = (B^2 + C^2- A^2)/BC
Which rule you use depends on what information you have been given. For example, if you have been given the length of three sides of a triangle and are trying to find the size of an angle, you would use the cosine rule - in this case the sine rule wont help you.
In some cases, you can use either rule. In general, the sine rule is easier to use, but since sin(A) = sin (180-A), sometimes the sine rule will yield an ambiguous answer.
In some cases, you can use either rule. In general, the sine rule is easier to use, but since sin(A) = sin (180-A), sometimes the sine rule will yield an ambiguous answer.