COS Function in Excel: Cosine of an Angle

COS Function in Excel: Cosine of an Angle featured illustration

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⏱ 2 min readUpdated 5 October 2026

MathLevel: IntermediateAvailable in: Excel 2007+

In this article
  1. Syntax
  2. Examples
  3. Example 1
  4. COS in practice
  5. Where you will use it
  6. Worked example
  7. Mistakes people make
  8. Related functions
  9. Continue learning

COS also expects radians. Seasonal models sometimes use SIN and COS of the month to capture yearly cycles.

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Syntax

=COS(number)
Argument What it means
number Angle in radians.

Examples

Example 1

=COS(2*PI()*MONTH(A2)/12)

A smooth yearly-cycle feature for a forecast model.

COS in practice

Where you will use it

  • Horizontal component of a force or slope
  • Draw circles and charts with formulas
  • Navigation and distance formulas

Worked example

DegreesFormulaResult
0=ROUND(COS(RADIANS(A2)),4)1
60=ROUND(COS(RADIANS(A3)),4)0.5
90=ROUND(COS(RADIANS(A4)),4)0

Results calculated in Excel.

Mistakes people make

MistakeWhat to do instead
Passing degrees directlyCOS expects radians: COS(RADIANS(60))
Tiny values instead of 0Round the result; floating point gives 6E-17 for 90°

SIN · PI

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📎 Practice files for this article

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    Practice workbook: Math & rounding24 tasks on realistic sales data — type your formula, the Check column turns green when it is right. Answers sheet included.
    ⬇ XLSX · 35 KB

Free to use for learning. Files with macros (.bas) are plain text — import them with Alt+F11 → File → Import File, and always test on a copy.

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