Plimpton 322 contains a fragment from a proto-trigonometric table. The Babylonians discovered exact sexagesimal trigonometry at least 1500 years before the ancient Greeks discovered trigonometry. Babylonian exact sexagesmial trigonometry uses exact ratios and square ratios instead of approximation and angles. sciencedirect 
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Plimpton 322 - els-cdn.com
babylonian-tablet