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Unformatted text preview: Lecture 25: Section 4.1 Angles and Their Measure An angle is formed by rotating a ray around its end point. The starting position of the ray is the initial side of the angle, and the position after rotation is the terminal side of the angle. The endpoint of the ray is called the vertex . An angle u1D703 is said to be in standard position if its vertex is in the origin and its initial side coincides with the positive u1D465axis. x y If the rotation is in the counterclockwise direction, the angle is positive ; if the rotation is clockwise, the angle is negative . Angles u1D6FC and u1D6FD are coterminal angles if they have the same initial and terminal sides. x y x y A central angle is an angle whose vertex is at the center of a circle. Radian Measure Def. One radian is a measure of the central angle that intercepts an arc whose length is equal to the radius. Algebraically, this means that u1D703 = u1D460 u1D45F where u1D703 is measured in radians....
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 Spring '11
 Gentimis
 Algebra, Angles

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