Cos (2x-π/6) = cos (x-π/2

jawab

π =180
π/6 = 30
π/2= 90

cos (2x -30)= cos (x -90) = cos {-(90 - x)}
cos (2x - 30) = cos (90 - x)
2x  - 30 = 90 - x 
3x = 120 + k. 360  atau 3x = - 120 + k. 360
x = 40 + k. 120  atau  x = - 40 + k. 120
k = 0,1,2....

k = 0, x= 40 , x = -40
k = 1, x = 160, x = 80
k = 2 , x = 280, x = 200
k = 3 , x = 400 , x = 320

untuk 0 ≤ x ≤ 360
x = (40, 80, 160, 200, 280, 320)
atau
x = ²/₉ π, ⁴/₉  π, ¹⁰/₉ π, ¹⁴/₉ π , ¹⁶/₉ π