The expression "cos(A - B)" represents the cosine of the difference between two angles, A and B. It is a fundamental concept in trigonometry, used to simplify calculations involving angles. The formula for this expression is given by: cos(A - B) = cos(A)cos(B) + sin(A)sin(B). This relationship helps in breaking down complex trigonometric problems into simpler parts. Understanding "cos(A - B)" is essential in various fields, including physics, engineering, and computer graphics. It allows for the analysis of waveforms, rotations, and oscillations. By applying this formula, one can easily compute the cosine of the difference between any two angles, enhancing problem-solving skills in mathematics.