cos^4 50° - cos^4 40°=
Matematika
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Pertanyaan
cos^4 50° - cos^4 40°=
1 Jawaban
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1. Jawaban nasril8
cos^4 50 - cos^4 40
= ( cos^2 50 + cos^2 40) (cos^2 50 - cos^2 40)
= 1 ( cos^2 50 - cos^2 40 )
= (cos 50 + cos 40) (cos 50 - cos 40)
= 2cos1/2(50+40)cos1/2(50-40) (-2sin1/2(50+40)sin1/2(50-40)
= ( 2cos 45.cos 10) (-2sin 45.sin 10)
= (akar 2.cos 10) ( -akar 2.sin 10 )
= -2 cos 10.sin 10
= - (2 cos 10. sin 10)
= - 2 sin 20°