The Excel COS Function

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Cosine of an Angle

For the simple right-angled triangle below, the cosine of the angle θ, is the ratio of the adjacent side, a, to the hypotenuse, h.

i.e. for the triangle above,

The trig. ratios are discussed further on the Wikipedia Trigonometric Ratios Page

Related Functions :

SIN Function

TAN Function

Basic Description

The Excel COS function calculates the cosine of a given angle (which is supplied in radians).

The format of the function is :

COS( Number )

Where the Number argument is the angle, in radians, that you want to calculate the cosine of.

Converting from Degrees to Radians

If your angle is in degrees, you will need to convert it into radians before supplying it to the cos function.

The easiest way to do this is to use the Excel Radians function:

=RADIANS( Degrees )

Examples of this are given below.

Example

Column B of the spreadsheet below, shows examples of the Excel Cos Function, used to calculate the cosine of different angles, which are in either degrees or radians.

The formulas are shown in the spreadsheet on the left and the results are shown in the spreadsheet on the right.

Formulas