Himpunan penyelesaian cos (2x + 15) = 1/2

cos (2x + 15) = 1/2
cos (2x + 15) = cos60
(2x + 15) = 60
2x = 60-15
2x =45
2x = 45/2
X= 22.5
Atau
cos (2x + 15) = cos300
(2x + 15) = 300
2x = 300-15
2x =285
2x = 285/2
X= 142.5