I have made some research and did not find this topic already, sorry if this has already been discussed somewhere.
The case of triangles with an angle of $60$ degree is special since there is a relation on sides which is quite close to the Pythagorean equality ($c^2=a^2+b^2-ab$), and there is also a formula for triangles with an angle of $120$ degrees. This is trivial using trigonometry and remains quite easy without it, using similar triangles and a few tricks. So my question is : it is known when was this result studied/written for the first time and was it long before the study of trigonometry? Thanks in advance for your comments.