Arcsec (or inverse secant) is the inverse function of secant. Since secant is 1/cos, arcsec(x) is equivalent to arccos(1/x). The domain is |x| ≥ 1 (x must be ≥ 1 or ≤ -1), effectively the opposite of the cos/sin domain.
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Pro Tips
The input value must be either ≥ 1 or ≤ -1.
Arcsec(1) = 0 degrees.
As x goes to infinity, arcsec(x) approaches 90 degrees.
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Fun Facts
"The secant function was named for the Latin 'secare', meaning 'to cut', because it cut across the circle."
"Arcsec is less common in everyday math but vital in integral calculus and engineering mechanics."
"In a right triangle, secant is the ratio of Hypotenuse to Adjacent side."
