nilai dari sin 15 derajat =

sin (A-B) = sin A. cos B - cos A. sin B

sin 15° = sin(45 - 30)°

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

sin (45-30)
=sin 45.cos30-cos45.sin30
=[tex] \frac{1}{2} \sqrt{2} - \frac{1}{2} \sqrt{3} - \frac{1}{2} \sqrt{2} \frac{1}{2} [/tex]
=[tex] \frac{1}{2} \sqrt{6} - \frac{1}{2} \sqrt{2} [/tex]
=[tex] \frac{1}{2} ( \sqrt{6} - \sqrt{2} )[/tex]