asec (x)

Arc secant, inverse secant

This is the inverse function for sec (x) usually defined as :

for any x and y such that
(x <= -1 or x >= 1), (0 <= y <= pi and y <> pi/2),
y = asec(x) if and only if x = sec(y)

more info with wikipedia...

 

 

 

x  :  to     
y  :  to