Jika A+B=pi/3 dan cos A cos B = 5/8, nilai cos (A-B)
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Pertanyaan
Jika A+B=pi/3 dan cos A cos B = 5/8, nilai cos (A-B)
1 Jawaban
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1. Jawaban QueenD
a+b = pi/3 = 60 °
Cos (a+b) = Cos a cos b - sin a sin b
cos 60 = 5/8 - sin a sin b
1/2 = 5/8 - sin a sin b
- sin a sin b = 1/2 - 5/8
- sin a sin b = 4/8 - 5/8 = -1/8
cos (a-b) = cos a cos b - sin a sin b
= 5/8 - 1/8 = 4/8 = 1/2
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