Generate the cosine graph by the unit circle. See also:
[b]Unit Circle and Sine Graph: [/b]http://www.geogebratube.org/material/show/id/8028
[b]Unit Circle and Cosine Graph: [/b] http://www.geogebratube.org/material/show/id/8029
[b]Defining Trigonometric Ratios:[/b] http://www.geogebratube.org/material/show/id/8088
Anthony Or. Education Bureau, Hong Kong.
E-mail: orchiming@gmail.com
