Plis tolong bantu kak

cos 120 = cos (180-60)
cos 120 = -cos 60
cos 120 = -1/2

sin 210 = sin (180+30)
sin 210 = -sin 30
sin 210 = -1/2

tan 315 = tan (360-45)
tan 315 = -tan 45
tan 315 = -1

-1/2 - (-1/2) + (-1)
-1