Trigonometry is not the work of one man or nation. Its history is thousands of years old and is part of every great civilization.
From Hipparchus to modern times there was no trigonometric "reason." Instead, the Greeks and later the Hindus and Muslims used trigonometric lines. These lines first took the form of strings and later half strings, or sines.
Then these sine strings and lines would be associated with numerical values, possibly approximations, and listed in trigonometric tables.