Trigonometry For Dummies
Book image
Explore Book Buy On Amazon

The trig functions can be defined using the measures of the sides of a right triangle. But they also have very useful definitions using the coordinates of points on a graph. First, let let the vertex of an angle be at the origin — the point (0,0) — and let the initial side of that angle lie along the positive x-axis and the terminal side be a rotation in a counterclockwise motion. Then, when the point (x,y) lies on a circle that’s intersected by that terminal side, the trig functions are defined with the following ratios, where r is the radius of the circle.

image0.jpg

About This Article

This article is from the book:

About the book author:

Mary Jane Sterling is the author of Algebra I For Dummies and many other For Dummies titles. She has been teaching mathematics at Bradley University in Peoria, Illinois, for more than 30 years and has loved working with future business executives, physical therapists, teachers, and many others.

This article can be found in the category: