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Excel COS Function

Excel COS function
Summary 

The Excel COS function returns the cosine of an angle given in radians. To supply an angle to COS in degrees, use the RADIANS function to convert to radians.

Purpose 
Get the cosine of an angle provided in radians.
Return value 
The cosine value
Syntax 
=COS (number)
Arguments 
  • number - The angle in radians for which you want the cosine.
Usage notes 

The COS function returns the cosine of an angle provided in radians. In geometric terms, the cosine of an angle returns the ratio of a right triangle's adjacent side over its hypotenuse. For example, the cosine of PI()/6 radians (30°) returns the ratio 0.866.

=COS(PI()/6) // Returns 0.886

Using Degrees

To supply an angle to COS in degrees, multiply the angle by PI()/180 or use the RADIANS function to convert to radians. For example, to get the COS of 60 degrees, you can use either formula below:

=COS(60*PI()/180)
=COS(RADIANS(60))

Explanation

Graph of Cosine Function

The graph of cosine above visualizes the output of the function for all angles from 0 to a full rotation. Geometrically, the function returns the x-component of the point corresponding to an angle on the unit circle. Since the cosine of an angle returns a ratio, the output of the function will always be in the range [-1, 1].

Graph courtesy of wumbo.net