Errors in handwritten solutions to Assignment 2

Number 1a) the final expression for the second derivative should have been (6-2t) / t⁵

Number 1d) the second derivative d²y / dx² = 2 - 4t²

Number 2c) the graph is restricted to allow x from -Pi / 2 to Pi / 2 only, because of the definition x = tan^-1 t