The formula of seca function is seca= 1/cosa, seca refers to a right triangle, and the ratio of the hypotenuse to the adjacent side of an acute angle is called acute seca, which is expressed by sec (angle). Secant is the reciprocal of cosine function.

Mathematical symbol secant is secant, which comes from English secant. Mathematician Gillard first used this symbol in his book Trigonometry. On the unit circle, the secant function is located on the secant, so this function is named secant function. Like other trigonometric functions, secant functions can be extended to complex numbers.