RASCOE: And Professor Hasting said that the cosine function definitely does not do this for sine, so does sine even have an inverse function?

The second solution is excluded by the traditional definition of the inverse cosine function (which, for arccos (x) = y, specifies a range of 0 <= y < pi so that the inverse cosine function can ...

E.g. the inverse of × 5 is ÷ 5. The inverse process undoes the original process. function of sin, cos or tan. The inverse functions of sin, cos and tan are sin⁻¹, cos⁻¹ and tan⁻¹.