nilai 4 cos pi/7.cos pi/5
Matematika
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Pertanyaan
nilai 4 cos pi/7.cos pi/5
1 Jawaban
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1. Jawaban Anonyme
TriGonoMetRi
2 cos a cos b = cos (a + b) + cos (a - b)
a = π/7 ; b = π/5
4 cos π/7 cos π/5
= 2 . 2 cos π/7 cos π/5
= 2 (cos (π/7 + π/5) + cos (π/7 - π/5))
= 2 (cos 12π/35 - cos 2π/35)