cos 4x = cos 1/3π, 0≤×≤2π

cos 4x = cos 1/3.180° cos 4x = cos 60° • 4x = 60° + k.360° x = 15° + k.90° untuk k=0 -> x=15° k=1 -> x=105° k=2 -> x=195° k=3 -> x=285° • 4x = -60° + k.360° x = -15° + k. 90° untuk k=0 -> x= -15° (TM) k=1 -> x=75° k=2 -> x=165° k=3 -> x=255° Hp = {15°, 75°, 105°, 165°, 195°, 225°, 285°} semoga membantu🤗