Nilai sin15° + sin 75° / cos15° - cos 105° =

= 2.sin {(15+75)/2}.cos {(15-75)/2)} / -2.sin {(15+105)/2}.sin {(15-105)/2}
= 2.sin 45 . cos -30 / -2.sin 60 . sin -45
= 2.sin 45 . cos 30 / -2.(-sin 45) . sin 60
= 2.sin 45 . sin (90-30) / 2.sin 45 . sin 60
= 2.sin 45 . sin 60 / 2.sin 45 . sin 60
= 1