> Napier’s main motivation was to find an easier way to do multiplication and division.
> Next, mathematicians decided to combine these tables. If you wanted to multiply trigonometric functions, you could find the values in a trigonometric table and then convert them to logarithms.
Actually, Napier's 1614 Mirifici Logarithmorum Canonis Descriptio contains tables of −10⁷ ln(sin x/10⁷) [0]. Non-trigonometric log tables appeared later.
> Napier’s main motivation was to find an easier way to do multiplication and division.
> Next, mathematicians decided to combine these tables. If you wanted to multiply trigonometric functions, you could find the values in a trigonometric table and then convert them to logarithms.
Actually, Napier's 1614 Mirifici Logarithmorum Canonis Descriptio contains tables of −10⁷ ln(sin x/10⁷) [0]. Non-trigonometric log tables appeared later.
[0] https://jscholarship.library.jhu.edu/bitstream/handle/1774.2...