#' Calculates the shear modulus (G) from two of the three other elastic moduli: bulk modulus (K), Young's modulus (E), or Poisson's ratio (\(\nu\)). Assumes 3D material properties.
The relationships used are: $$G = \frac{3KE}{9K - E}$$ $$G = \frac{3K(1 - 2\nu)}{2(1 + \nu)}$$ $$G = \frac{E}{2(1 + \nu)}$$