삼각법 예제

$\cos (\frac{7 π}{12}) \cos (\frac{5 π}{12}) + \sin (\frac{7 π}{12}) \sin (\frac{5 π}{12})$

단계 1

$\cos (\frac{7 π}{12}) \cos (\frac{5 π}{12}) + \sin (\frac{7 π}{12}) \sin (\frac{5 π}{12})$