BENTUK PERKALIAN DAN PANGKAT
\(2 \sin A \:.\: \cos B = \sin (A + B) + \sin (A - B)\)
\(2 \cos A \:.\: \sin B = \sin (A + B) - \sin (A - B)\)
\(2 \cos A \:.\: \cos B = \cos (A + B) + \cos (A - B)\)
\(- 2 \sin A \:.\: \sin B = \cos (A + B) - \cos (A - B)\)