Possible error introduced in version 4.0.2, in formula from Book 1 Section 11.2

[FelipeMoleiro]

On this section there are two equations about the refracted vector. They are as follows:

Apparently they used to be different in v4.0.1:

Which makes sense if we assume that R (and subsequently R') are unit vectors. The problem is that this was not stated as a condition previously in this chapter and for that reason the first equation was changed in version 4.0.2 due to issue #1644 and fixed on commit #1645.

The issue I possibly encountered in this version is that the second equation appears to also assumes the unit vector, but that equation was not changed in that commit.

I believe that the second equation, without assuming the unit vector, should be:

or:

Would that be correct?

[hollasch]

I agree. I believe the correct approach is to present the equations for general (possibly non-unit) vectors, and then give the equations again, but for cases where $R$ is a unit vector.