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Unformatted text preview: 1 Trigonometry Information Angles 1. An angle has an initial side and a terminal side. A positive angle rotates counterclockwise and a negative angle rotates clockwise. Angles that look the same but only differ by number of rotations either direction are called coterminal angles . These angles may be found by adding or subtracting multiples of 360° or 2 π . 2. A radian is the measurement of a central angle (angle in standard position in a circle) whose measure of the radius of the circle (sides of the angle) equals the length of the arc of the circle that the angle subtends. One radian is approximately 57.3°. If no label is present, the measurement is assumed to be radians. ( ) 180 180 360 2 180 1 1 π π π π = = = = r r r r 3. To convert degrees to radians: Multiply the degree measurement by 180 π r . To convert radians to degrees: Multiply the radian measurement by 180 π r . 4. Commonly used angles: 6 4 3 3 2 2 30 45 60 90 180 270 360 2 π π π π π π π = = = = = = = = r r r r r r r r 5. The relationship between a central angle of θ in radians (angle in standard position), the length of the radius r of the circle (side), and the length of the subtended arc s is s r θ = . The relationship between a central angle of θ in radians , the length of the radius r of the circle (side of the angle), and the area of the sector of the circle subtended by the angle is 2 1 2 A r θ = . 6. There are six trigonometric functions, where an angle is degrees or radians is paired with a ratio (number). These functions are sine (sin), cosine (cos), tangent (tan), cosecant (csc), secant (sec), and cotangent (cot)....
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 Spring '08
 DELWORTH
 Algebra, Trigonometry, Angles, tan θ

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