nilai perbandingan dr cos π/12

[tex] \frac{\pi}{12} = {15}^{0} \\ \\ \cos( {15}^{0} ) = \cos(45^{0} - 30^{0}) \\ = \cos(45^{0}) \cos(30^{0}) + \sin(45^{0}) \sin(30^{0}) \\ = \frac{1}{2} \sqrt{2} . \frac{1}{2} \sqrt{3} + \frac{1}{2} \sqrt{2} . \frac{1}{2} \\ = \frac{1}{4} ( \sqrt{6} + \sqrt{2} )[/tex]