1. The equation giving the nth function in a class of special functions in terms of the nth derivatives of some polynomial.

2. The formula dn + k dr = 0, expressing the difference dn in the unit normals to a surface at two neighboring points on a line of curvature, in terms of the difference dr in the position vectors of the two points and the principal curvature k.

3. The formula for a matrix that is used to transform the cartesian coordinates of a vector in three-space under a rotation through a specified angle about an axis with specified direction cosines.