In ncollide we have an IsometryOps trait that defines the lerp_slep method for isometry interpolation. This interpolation uses linear interpolation for the translation part of the isometry, and spherical interpolation for its angular part.

We should add this lerp_slerp method directly to nalgebra's `Is

UPDATE: almost all of the points below have been taken care of, all that remains is to add mathematically complete definitions for vector spaces and algebras to section 6.1 and 6.2 in the tutorial.

Suggested fixes for "GAP -- A Tutorial Release 4.11.0, 29-Feb-2020"

On page 41, in the first sentence after the first Example

improve HarmonicNumber implementation:
https://github.com/axkr/symja_android_library/blob/master/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/Arithmetic.java#L1834

• https://en.wikipedia.org/wiki/Harmonic_number
• https://medium.com/cantors-paradise/the-celebrated-harmonic-numbers-and-how-to-approximate-them-b8747a4efeec