It's multi-valued, I suppose. tan^-1 (tan (x)) is equal to x plus any integer multiple of pi (or of 180°). Same for the other pairs of functions. But one of the

It's multi-valued, I suppose. tan^-1 (tan (x)) is equal to x plus any integer multiple of pi (or of 180°). Same for the other pairs of functions. But one of the values results in a division by zero.