sin 75 - sin 15 / cos 105 - cos 15

pembilang dulu ya
= 2 cos 1/2 (75+15) sin 1/2 (75-15)
= 2 cos 45 sin 30
= 2 . 1/2√2 . 1/2
= 1/2 √2

penyebut:
= -2 sin 1/2 (75+15) sin 1/2 (75-15)
= -2 sin 45 sin 30
= -2. 1/2√2 . 1/2
= -1/2√2

Maka, Sin 75 - sin 15 / cos 105 - cos 15 = -1