1.1.15 Vector Algebra

Problem: Find the cosine of the angle between the vectors \( \overrightarrow{A B} \) and \( \overrightarrow{A C} \). \[ A(0 ; 2 ;-4), \quad B(8 ; 2 ; 2), \quad C(6 ; 2 ; 4) \text {. } \]