Cosine function

The cosine function describes a specific relationship in a circle: it measures the horizontal distance from the center to a point on the circle as you rotate around it. Imagine a circle and an angle starting from the rightmost point; as you rotate this angle, the cosine value tells you how far along the horizontal axis the moving point is from the center. It varies smoothly between 1 and -1 as the angle completes full rotations, capturing oscillatory behavior seen in waves, sound, and signals, making it fundamental in mathematics, physics, and engineering.