The cosine function (cos) is a fundamental trigonometric function that relates an angle in a right triangle to the ratio of the length of the adjacent side to the hypotenuse. Mathematically, it is defined as: cos(θ) = Adjacent Side / Hypotenuse in a right triangle. 1 On the unit circle, it corresponds to the x-coordinate of a point on the circle's circumference. 1 The range of the cosine function is between -1 and 1, and it is a periodic function with a period of 2π radians. 2 The cosine function is widely used in various applications, including geometry, physics, and engineering. 2
