cos 4x + 3 cos 2x-1 = 0, 0
Matematika
masfaridz
Pertanyaan
cos 4x + 3 cos 2x-1 = 0, 0<x<(phi)
1 Jawaban
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1. Jawaban nasril8
cos 4x + 3 cos 2x - 1 = 0
cos (2x+2x) + 3cos 2x - 1 = 0
2cos^2 2x - 1 + 3cos 2x - 1 = 0
2cos^2 2x + 3cos 2x - 2 = 0
(2cos 2x -1 ) (cos 2x +2 ) = 0
2cos 2x - 1 = 0, atau cos 2x + 2 = 0
2cos 2x = 1 , atau cos 2x = -2 (tidak ada cos yang bernilai -2.
cos 2x = 1/2
cos 2x = cos 60°,120°
2x = 60° + 2k.phi
x = 30 + k.phi
x = 30
2x = 120 + 2k.phi
x = 60 + k.phi
x = 60
HP = { 30°, 60° }