Purpose
Return value
Syntax
=SEC(number)- 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:
=SIN(60*PI()/180)
=SIN(RADIANS(60))
Explanation
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:
=SEC(angle)=1/COS(angle)
The relationship between SEC and COS is visualized in the graph of both of the functions shown below:
Images courtesy of wumbo.net.
Related functions
COS Function
The Excel COS function returns the cosine of an angle given in radians. To supply an angle to COS in degrees, use the RADIANS function to convert to radians.
CSC Function
