Question: when was trigonometry first thought to be used
[{'answer': '2nd millennium BC', 'provenance': [{'wikipedia_id': '6785051', 'title': 'History of trigonometry', 'start_paragraph_id': 1, 'start_character': 46, 'end_paragraph_id': 1, 'end_character': 63, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '6785051', 'title': 'History of trigonometry', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 916, 'bleu_score': 0.6627741749857581, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16389273543963223688}, 'section': 'Section::::Abstract.'}]}]