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Excel SEC Function

Excel SEC function
The Excel SEC function returns the secant of an angle provided in radians.
Get secant of an angle
Return value 
The secant value.
=SEC (number)
  • number - The angle in radians for which you want the secant.
Usage notes 

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 wumbo.net.

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