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Cosine Calculator for Degrees or Radians

Written by:
PK

On this page is a cosine calculator, for either angles or degrees. Enter an angle's measurement, choose the units, and run the calculator to see the cosine.

Cosine Calculator for Angles or Radians

Using the Cosine Calculator

To use the tool to find the cosine, enter the measurement of the angle in either degrees or radians, choose the units, and compute.

  • Angle - measurement of the angle (in degrees or radians)
  • Degrees or Radians? - use the menu to choose the units

Once you're happy with the inputs, click the "Compute Cosine" button.

  • Cosine - the cosine, or ratio of the adjacent side over the hypotenuse

What is the cosine?

For a given angle in a right triangle, cosine is the ratio of the adjacent side to the longest side, or hypotenuse.

Since the hypotenuse is longest, the adjacent side can be – at max – equal to the hypotenuse. It follows that cosine is always less than or equal to 1.

Right triangle to illustrate trigonometry functions
Right Triangle Diagram (CC By-SA 3.0 Wikimedia)

Beyond triangles, trigonometric functions can be used to find the ratio between sides of a unit circle – a circle with radius 1.

Unit Circle to illustrate trigonometry.
Unit circle diagram (CC By-SA 3.0 Wikimedia)

Cosine as a formula

As a trigonometry formula, cosine is usually abbreviated as "cos", as in the following equation:

\cos(\theta)

If you know the result of the cosine function, you can use arccos or the inversecosine to find the angle.

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