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How to Use the COS Function in Excel

We can use the Excel COS function when looking for a cosine of an angle in radians. We can supply an angle to COS in degrees by simply multiplying the angle by PI()/180. To get it in radians, we can simply use the RADIANS function in excel. This post provides a summary of how to use the COS function in excel.

Figure 1: How to use the COS function in Excel

General syntax of the formula



  • Number- refers to the angle for which we want to find the cosine, the angle should be in radians.

Understanding the formula

  • The COS function only accepts angles in radians if it is to return the correct answer.
  • For us to supply the angle in specified degrees, we have to multiply the angle by PI()/180.
  • We can also use the RADIANS function in order to convert the angle into radians.

In the example above, we have the cosine of the 60 degrees as 0.5 as shown in cell B2. The formula of how we have arrived at the results in the example are shown in column C.

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