 The interval [−1,1], with length two, demarcated by the positive and negative units, occurs frequently, such as in the range of the trigonometric functions sine and cosine and the hyperbolic function tanh.This interval may be used for the domain of inverse functions.For instance, when θ is restricted to [−π/2, π/2] then sin(θ) is in this interval and arcsine is defined there.