Cosine Calculator
Calculate the cosine of any angle in degrees or radians. Get the cos value, its inverse (arccos), the secant, and related angle information.
The cosine function is a fundamental trigonometric function. For a right triangle, cos(θ) equals the ratio of the adjacent side to the hypotenuse. On the unit circle, cos(θ) gives the x-coordinate of the point at angle θ.
The cosine function has a range of [-1, 1] and a period of 360° (2π radians). Key values include cos(0°) = 1, cos(30°) = √3/2 ≈ 0.8660, cos(45°) = √2/2 ≈ 0.7071, cos(60°) = 0.5, and cos(90°) = 0. Cosine is positive in Quadrants I and IV, and negative in Quadrants II and III.
The inverse cosine function, arccos(x) or cos⁻¹(x), returns the angle whose cosine is x. It is defined for x in [-1, 1] and returns values in [0°, 180°] (or [0, π] radians). The secant, sec(θ) = 1/cos(θ), is the reciprocal of cosine and is undefined when cos(θ) = 0 (at 90° and 270°).