himpunan penyelesaian 1 - akar 2 cos (2x - pi/4) = 0 untuk 0 kurang dari atau sama denga x kurang dari atau sama dengan 2pi

1 - √2 cos (2x - π/4) = 0
-√2 cos (2x - π/4) = -1
cos (2x - π/4) = -1/-√2
cos (2x - π/4) = 1/√2
cos (2x - π/4) = cos π/4
2x - π/4 = π/4
2x = π/4 + π/4
2x = π/2
x = π/4
cos (2x - π/4) = cos (7/4)π
2x - π/4 = (7/4)π
2x = (7/4)π + π/4
2x = 2π
x = π
cos (2x - π/4) = cos (9/4)π
2x - π/4 = (9/4)π
2x = (9/4)π + π/4
2x = (10/4)π
x = (10/8)π
x = (5/4)π
cos (2x - π/4) = cos (15/4)π
2x - π/4 = (15/4)π
2x = (15/4)π + π/4
2x = 4π
x = 2π
maka himpunan penyelesainnya
{π/4 , π , (5/4)π , 2π}