The 4th millennium BC.
The third millennium BC.
It is believed that arches appeared as early as the 2nd millennium BC in Mesopotamia.
The 4th millennium BC began 4000 BC and ended in 3000 BC. The 4th millennium BC marks the beginning of the bronze age and of writing.
Every millennium, including the 5th millennium BC, is 1000 years.
2nd millennium
Damascus, Syria having first been settled in the 2nd Millennium BC.
The 2nd Millennium began in the year 1001.
4th millennium BC through 2000 BC
If you are asking what culture first developed trigonometry, the study of triangles can be traced back to the Egyptians and Babylonians as early as the 2nd millennium BC.
From the year 1001 to 2000.
It was a very long time ago in the bc land.