Jika A+B = 2Π/3 dan cos A.cos B = 3/8, nilai cos (A-B)=
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Pertanyaan
Jika A+B = 2Π/3 dan cos A.cos B = 3/8, nilai cos (A-B)=
1 Jawaban
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1. Jawaban Anonyme
TriGonoMetRi
A + B = 2/3 π = 120°
cos (A + B) = cos 120°
cos A cos B - sin A sin B = -1/2
3/8 - sin A sin B = -1/2
sin A sin B = 3/8 + 1/2 = 7/8
Maka,
cos (A - B)
= cos A cos B + sin A sin B
= 3/8 + 7/8
= 10/8
= 5/4