Hasil dari sin 28°. Sin 58°

[tex]
\sin{28\degree}\cdot\sin{58\degree}=-\frac{1}{2}(\cos{(28\degree+58\degree)}-\cos{(28\degree-58\degree)})=-\frac{1}{2}\cos{86\degree}+\frac{1}{2}\cos{(-30\degree)}=-\frac{1}{2}\sin{4\degree}+\frac{1}{2}\cdot\frac{1}{2}\sqrt{3}[/tex]