Generate the cosine graph by unit circle. See also:
[b]Unit Circle and Sine Graph: [/b]http://www.geogebratube.org/material/show/id/8028
[b]Unit Circle and Tangent Graph: [/b]http://www.geogebratube.org/material/show/id/8030
[b]Defining Trigonometric Ratios: [/b]http://www.geogebratube.org/material/show/id/8088
Anthony Or. GeoGebra Institute of Hong Kong.
E-mail: orchiming@gmail.com
