Trigonometry is the branch of mathematics that is concerned with calculating the angles of triangles or the lengths of their sides.
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Trigonometry is the branch of mathematics that is concerned with calculating the angles of triangles or the lengths of their sides.
N-UNCOUNT
Collins COBUILD. Толковый словарь английского языка для изучающих язык Коллинз COBUILD (международная база данных языков Бирмингемского университета) . 2012