TRIGONOMETRI

1]

cos 3x = cos ½ π , 0 < x < π

cos 3x = cos 90°

cos 3x = 0

cos α bernilai 0 saat α = π/2 dan α = π + π/2 = 3π / 2 (tidak memenuhi)

3x = π/2

x = π/6

HP : {π/6}

2]

sin 2x = - ½ √2 , 0 < x < 2π

sin α bernilai negatif saat berada di kuadran 3 dan kuadran 4

sin π/4 = ½√2

kuadran 3 :

sin (π + π/4) = - sin π/4

sin 5π/4 = - ½ √2

kuadran 4 :

sin (2π - π/4) = - sin π/4

sin 7π/4 = - ½ √2

sin α bernilai - ½√2 saat α = 5π/4 dan α = 7π/4

2x = 5π/4

x = 5π/8

2x = 7π/4

x = 7π/8

HP : {5π/8 , 7π/8}