The Excel SEC function returns the secant of an angle — the reciprocal of the cosine, 1/COS. Excel measures angles in radians, so convert degrees with RADIANS first.
Syntax
| Argument | Description | |
|---|---|---|
number | Required | The angle in radians whose secant you want. Convert degrees with RADIANS(deg) or deg*PI()/180. |
How to use it
SEC is simply 1/COS(number), introduced in Excel 2013 as a shorthand. Excel expects radians, so wrap any degree value in RADIANS():
Because secant is the reciprocal of cosine, =SEC(x) gives exactly the same result as =1/COS(x) — handy if you're working in an older version without SEC.
Undefined where cosine is zero. At 90° the cosine is zero, so secant is undefined and =SEC(RADIANS(90)) returns a very large finite number from floating-point rounding rather than a clean value.
Try it: interactive demo
Pick a SEC example to see the formula and its result.
Practice workbook
Frequently asked questions
What is the secant of an angle?
SEC(x) = 1/COS(x). So if the cosine of an angle is 0.5, its secant is 2.Which Excel versions have SEC?
=1/COS(x) instead.Does SEC take degrees or radians?
RADIANS(deg), for example =SEC(RADIANS(60)).Why does SEC sometimes return a huge number?
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