The Excel SEC function returns the secant of an angle provided in radians.


Get secant of an angle

Return value 

The secant value.


  • number - The angle in radians for which you want the secant.

How to use 

The SEC function returns the secant of an angle provided in radians. In geometric terms, the secant of a right-triangle's angle is equal to the ratio of the length of its hypotenuse over the length of its adjacent side. For example, the secant of PI()/6 (30°) returns the ratio 1.514.

=SEC(PI()/6) // Returns 1.514

Using Degrees

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



Graph of Secant Function

The graph of SEC, shown above, visualizes the output of the function for angles from 0 to a full rotation. The function has two vertical asymptotes at π/2 and 3π/2 respectively where the output of the function diverges to infinity. The SEC function is the reciprocal of COS and can be equivalently defined in the formula below:


The relationship between SEC and COS is visualized in the graph of both of the functions shown below:

Graph of Secant and Cosine Function

Images courtesy of

Dave Bruns Profile Picture

AuthorMicrosoft Most Valuable Professional Award

Dave Bruns

Hi - I'm Dave Bruns, and I run Exceljet with my wife, Lisa. Our goal is to help you work faster in Excel. We create short videos, and clear examples of formulas, functions, pivot tables, conditional formatting, and charts.