Sumerian astronomers studied angle measure, using a division of circles into 360 degrees. They, and later the Babylonians, studied the ratios of the sides of See more

Using the unit circle, one can extend the definitions of trigonometric ratios to all positive and negative arguments (see trigonometric function).
Graphs of … See more

Astronomy
For centuries, spherical trigonometry has been used for locating solar, lunar, and stellar positions, … See more

• Aryabhata's sine table
• Generalized trigonometry
• Lénárt sphere
• List of triangle topics
• List of trigonometric identities See more

Trigonometric ratios are the ratios between edges of a right triangle. These ratios depend only on one acute angle of the right triangle, since any two right triangles with the same acute angle are similar.
So, these ratios define See more

Trigonometry has been noted for its many identities, that is, equations that are true for all possible inputs.
Identities involving only angles are known as trigonometric … See more

• Boyer, Carl B. (1991). A History of Mathematics (Second ed.). John Wiley & Sons, Inc. ISBN 978-0-471-54397-8.
• Nielsen, … See more