>  1. Both `exact-integer-nth-root` and `exact-integer-log` assume its
'k' parameter to be an positive exact integer. Although these two
procedures will not return exact integers when k is not an exact
positive integer, it is still best to explicitly point this out.

exact-integer-nth-root allows k to be zero, because the nth root of zero
is defined, it would just return (values 0 0).

I've modified exact-integer-nth-root to require that `n` be positive,
however, because otherwise (exact-integer-nth-root 0 0) cannot satisfy
the requirements of the procedure.

 > 2. A parameter of `rationalize` are named `delta-upper`, but you refer
to it later with another name `delta-higher`.

Fixed.

 > 3. The math formulae of `angle` are wrong. …

Fixed.

 > The “z” in “angle z” is set in Roman typeface; to keep up with the
preceding text, these “z” should be set in italics.

Fixed. Thank you for the comments.

-- Peter McGoron