Nilai dari sin 75 derajat×sin 15 derajat =

sin(45+30).sin(45-30)
= (sin 45 cos 30 + sin 30 cos 45)(sin 45 cos 30 - sin 30 cos 45)
= (1/2√2 . 1/2√3 + 1/2 . 1/2√2)(1/2√2 . 1/2√3 - 1/2 . 1/2√2)
= (1/4√6+1/4√2)(1/4√6-1/4√2)
= (1/4√6)²-(1/4√2)²
= (1/16 x 6) - (1/16 x 2)
= 6/16 - 2/16
= 4/16
= 1/4