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.

You did it in radians. Try degrees.

Edit: (Or use 0.15708 instead of 9 in your link.)

I think the intended simplification is : (sin⁻¹(cos⁻¹(tan⁻¹(tan(cos(sin(9))))))−9)⁻¹ -> (sin⁻¹(cos⁻¹(cos(sin(9))))−9)⁻¹ -> (sin⁻¹(sin(9))−9)⁻¹ -> (9−9)⁻¹ -> 0⁻¹ -> 1/0