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Cosine rule help as well ?
Help and explanation please!
1 Answer
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- stanschimLv 73 months agoFavorite Answer
Cosine Rule: c^2 = a^2 + b^2 - 2ab(cos(C))
a is the side opposite angle A; b is the side opposite angle B; c is the side opposite angle C.
Substituting from the problem:
15^2 = 5^2 + x^2 - 2(5)(x)(cos(60))
225 = 25 + x^2 - 10x(cos(60))
200 = x^2 - 5x
x^2 - 5x - 200 = 0 (last answer)
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