This worksheet demonstrates the use of Maple for calculating constitutive coefficients of linear elastic materials (Hooke's law in the three-dimensional theory of elasticity) by means of coordinate transformations (rotation of coordinates). We start from an anisotropic material embedded in a right-handed orthogonal Cartesian coordinate system adopting Voigt's notation. In this case the starting object is a symmetric 6 by 6 matrix characterized by 21 independent coefficients.