NavList:

Bowditch  1958 p 1010 discusses the multiplication of negative numbers.

I have very quickly scanned Bowditch 1943 and cannot find a reference to negative numbers. But it was a very quick scan..........

In Bowditch 1995 there is a new chapter on navigational mathematics. Again after a very quick scan I cannot find a reference to negative numbers.

In Nicholls's Concise Guide vol 1 1930 the very first chapter is called Algebra.The introduction states:

'This chapter is intended as a "refresher" for those who may be a little backward in their algebra as a knowledge of the application and signs and symbols is essential to the manipulation of navigational quantities.'

Negative numbers are dscussed as is a ~ b

Are we applying 21st century thinking to a problem that probably did not exist i.e.  in pre-GPS and pre-calculator times navigators did not need to worry about negative numbers. So why should we?