Sin150+sin120:cos210-cos300

From sin (180-x) = sin (x)

sin (150) = sin (180-30) = sin (30)

sin (120) = sin (180-60) = sin (60)

from cos (360-x) = cos (x)

cos (300) = cos (360-60) = cos (60)

cos (210) = cos (360-150) = cos (150)

from cos (180-x) = - cos (x)

cos (210) = cos (150) = cos (180-30) = - cos (30)