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