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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 . 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 = = = = r r r r 3. To convert degrees to radians: Multiply the degree measurement by 180 r . To convert radians to degrees: Multiply the radian measurement by 180 r . 4. Commonly used angles: 6 4 3 3 2 2 30 45 60 90 180 270 360 2 = = = = = = = = r r r r r r r r 5. The relationship between a central angle of 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 = . The relationship between a central angle of 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 = . 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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