This article describes the formula syntax and usage of the SEC function in Microsoft Excel.
Description
Returns the secant of an angle.
Syntax
SEC(number)
The SEC function syntax has the following arguments.
Number Required. Number is the angle in radians for which you want the secant.
Remarks

The absolute value of number must be less than 2^27.

If the angle is in degrees, either multiply the angle by PI()/180 or use the RADIANS function to covert the angle to radians.

If number is outside of its constraints, SEC returns the #NUM! error value.

If number is a nonnumeric value, SEC returns the #VALUE! error values.
Example
Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.
Formula 
Description 
Result 
=SEC(45) 
Returns the secant of a 45 degree angle. 
1.90359 
=SEC(30) 
Returns the secant of a 30 degree angle. 
6.48292 