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Monday, June 10, 2013

Coterminal Angles

Category: Trigonometry

"Published in Suisun City, California, USA"

Find an angle between 0° and 360° that is coterminal with the given angle:

a. 2223°
b. -400°
c. 1270°
d. -800°

Solution:

Coterminal angles are angles in standard position (angles with the initial side on the positive x-axis) that have a common terminal side (angles less than 360°). Usually, coterminal angles are more than 360°. To simplify a coterminal angle, divide a given angle by 360° which is equivalent to 1 revolution. The remainder or a fraction of a revolution will be the terminal side. Let's have the examples of the following:

a. 2223°

    Since the given angle is positive, then it is rotated counterclockwise from positive x-axis (initial side) to terminal side.


After six complete revolution from positive x-axis in a counterclockwise direction, there's an excess angle of 



which is located at the first quadrant.

Photo by Math Principles in Everyday Life

b. - 400°

    Since the given angle is negative, then it is rotated clockwise from positive x-axis (initial side) to terminal side.


After one complete revolution from positive x-axis in a clockwise direction, there's an excess angle of


which is located at the fourth quadrant.

Photo by Math Principles in Everyday Life

c. 1270°

    Since the given angle is positive, then it is rotated counterclockwise from positive x-axis (initial side) to terminal side.


After three complete revolution from positive x-axis in a counterclockwise direction, there's an excess angle of 



which is located at the third quadrant.

Photo by Math Principles in Everyday Life

 d. - 800°

 Since the given angle is negative, then it is rotated clockwise from positive x-axis (initial side) to terminal side.


After two complete revolution from positive x-axis in a clockwise direction, there's an excess angle of


 which is located at the fourth quadrant.

 
Photo by Math Principles in Everyday Life