Trigonometry

Right triangle

Since the time of the Sumerians, about 3000 BC, scientists have studied the stars and the planets and tried to figure out the patterns in their movements. This was much harder because everybody thought that the stars and planets circled around the Earth, and really they don't. About 140 BC, the Greek astronomer Hipparchus of Rhodes - who still thought that the stars and planets went around the Earth - realized that you could use a system of imaginary right triangles connecting the Earth to the planet or star to calculate patterns in the planet or star's movements. This was the beginning of trigonometry.

To find out more about trigonometry, check out these books from Amazon.com or from your library: