Definition of secant
1 : a straight line cutting a curve at two or more points
2 : a straight line drawn from the center of a circle through one end of a circular arc to a tangent drawn from the other end of the arc
3a : a trigonometric function that for an acute angle is the ratio of the hypotenuse of a right triangle of which the angle is considered part and the leg adjacent to the angleb : a trigonometric function sec θ that is the reciprocal of the cosine for all real numbers θ for which the cosine is not zero and that is exactly equal to the secant of an angle of measure θ in radians
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