This article describes the formula syntax and usage of the COS function in Microsoft Excel.
Description
Returns the cosine of the given angle.
Syntax
COS(number)
The COS function syntax has the following arguments:

Number Required. The angle in radians for which you want the cosine.
Remark
If the angle is in degrees, either multiply the angle by PI()/180 or use the RADIANS function to convert the angle to radians.
Example
Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.
Formula 
Description 
Result 
=COS(1.047) 
Cosine of 1.047 radians 
0.5001711 
=COS(60*PI()/180) 
Cosine of 60 degrees 
0.5 
=COS(RADIANS(60)) 
Cosine of 60 degrees 
0.5 