'Helper method for set_coordinate_type. It calculates Lame coefficients
for given transformations equations.
Parameters
equations : tuple
Tuple of transformation equations'

def _calculate_lame_coefficients(self, equations):

    h1 = sqrt((((diff(equations[0], self.x) ** 2) + (diff(equations[1], self.x) ** 2)) + (diff(equations[2], self.x) ** 2)))
    h2 = sqrt((((diff(equations[0], self.y) ** 2) + (diff(equations[1], self.y) ** 2)) + (diff(equations[2], self.y) ** 2)))
    h3 = sqrt((((diff(equations[0], self.z) ** 2) + (diff(equations[1], self.z) ** 2)) + (diff(equations[2], self.z) ** 2)))
    return map(simplify, [h1, h2, h3])
