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Unformatted text preview: Section 4.3 – Unit Circle Trigonometry 1 Section 4.3 Trigonometric Functions of Angles An angle is formed by two rays that have a common endpoint (vertex). One ray is called the initial side and the other the terminal side . A terminal angle can lie in any quadrant, on the x-axis or y-axis. An angle is in standard position if the vertex is at the origin of the two-dimensional plane and its initial side lies along the positive x-axis. Positive angles are generated by counterclockwise rotation. Negative angles are generated by clockwise rotation. Section 4.3 – Unit Circle Trigonometry 2 The Reference Angle or Reference Number Let θ be an angle in standard position. The reference angle associated with θ is the acute angle (with positive measure) formed by the x-axis and the terminal side of the angle θ . When radian measure is used, the reference angle is sometimes referred to as the reference number (because a radian angle measure is a real number). Example 1: Draw each angle in standard position and specify the reference angle. a. 405 o Note: Notice that in part a. 405 terminates in the same position as 45 . These type of angles are called coterminal angles . Every angle has infinitely many coterminal angles. Every angle has infinitely many coterminal angles....
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This note was uploaded on 02/20/2012 for the course MATH 1330 taught by Professor Staff during the Fall '08 term at University of Houston.
- Fall '08