when measuring in radians, an angle of "θ" radians will correspond to an arc whose length is "rθ", where "r" is the radius of the circle. Thus in the unit circle, "the arc whose cosine is "x"" is the same as "the angle whose cosine is "x"", because the length of the arc of the circle in radii is the same as the measurement of the angle in radians. In computer programming languages, the inverse trigonometric functions are often called by the abbreviated forms asin, acos, atan.