‘Posit’ comes from the Latin positus meaning ‘it is put in place’. I guess the best translation is ‘Given:’

            The formula we learn for earth convergency is:

            Convergency           = change of long x sine mean latitude

            using the given terms,

            Convergency           = g x sine Lm or

= g.sin Lm, which is a shorthand version of the same thing.

Conversion angle is half convergency so

Conversion angle = (g.sin Lm)/2

This is not quite the same as g/2.sin Lm which easily could be interpreted as being g/(2 sin Lm) but it’s all we’ve got so, reluctantly,