The ancient Greeks were the first to develop the conceptual framework of trigonometry. The noted Greek astronomers Hipparchus, Menelaus and Ptolomy contributed in advancing the field.
Some scholars attributed the invention of trigonometry to Hipparchus. He was the first to formulate a table of chords. A "chord" in ancient Greece was used as a trigonometric function and applied in astronomy. By manipulating the chords on his table, Hipparchus was able to calculate the movement of the zodiac signs. Meanwhile, Menelaus was the first to introduce the spherical triangle along with some trigonometric ratios. Most historians believed that Ptolomy made no original contributions, rather he compiled the works of previous Greek astronomers and published them.