Jawabanmu

2014-06-15T19:55:00+07:00
Π = 180°
5/6 . π = 150°
2 π = 360°

2 cos ( 2x + 5/6.π) = √3
2 cos (2x + 150°) = √3
cos (2x + 150°) = 1/2 √3

1/2 √3 = cos 30°, cos 330°, cos 390°, cos 690°, cos 750°, cos 1050°....

2x + 150°= 30°
2x = -120°
x = -60°

2x + 150° = 330°
2x = 180°
x = 90°

2x + 150° = 390°
2x = 240°
x = 120°

2x + 150° = 690°
2x = 540°
x = 270°

2x + 150° = 750°
2x = 600°
x = 300°

2x + 150° = 1050°
2x = 900°
x = 450°

0°≤ x ≤ 360°

maka, x = {90°, 120°, 270°, 300°}







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