From the wiki of synthetic geometry [1]:
> Synthetic geometry (sometimes referred to as axiomatic geometry or even pure geometry) is the study of geometry without the use of coordinates *or formulae*. It relies on the axiomatic method and the tools directly related to them, that is, compass and straightedge, to draw conclusions and solve problems.
> Only after the introduction of coordinate methods was there a reason to introduce the term "synthetic geometry" to distinguish this approach to geometry from other approaches.
From wiki of analytic geometry [2]:
> In classical mathematics, analytic geometry, also known as coordinate geometry or Cartesian geometry, is the study of geometry using a coordinate system. This *contrasts* with synthetic geometry.
I know you’re using this to dismiss my case but the first line of Wikipedia hardly a standard for definition. Further down in the same article:
> *Usually* the Cartesian coordinate system is applied to manipulate equations for planes, straight lines, and squares, often in two and sometimes three dimensions.
> As taught in school books, analytic geometry can be explained more simply: it is concerned with defining and representing geometrical shapes in a numerical way and extracting numerical information from shapes' numerical definitions and representations.
Putting it together:
1. The classic western geometry was predominantly non-synthetic, with the term “synthetic” being introduced much later in order to differentiate pure geometry from Analytic/algebraic forms
2. Use of formulae is outside the scope of pure geometry ala Euclidian style.
3. Distances and angles are geometric shapes. Trigonometry using algebra is part of analytic geometry.
4. Indian mathematicians used formulae and algebraic manipulations to arrive at geometric insights, including developing trigonometric identities and series.
5. Explicit use of coordinate system is not essential. It’s “usually” used.
6. Descartes didn’t invent the number line. He only proposed a coordinate system. Number line itself was a much later development. Descartes’ coordinates were a lot more abstract.
If using the modern coordinate system is your criteria for analytic geometry, when was it finally established?
What am I missing? Genuinely curious and happy to be completely wrong here.
[1] https://en.wikipedia.org/wiki/Synthetic_geometry
[2] https://en.wikipedia.org/wiki/Analytic_geometry