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Trigonometric Ratios of an Obtuse Angle

Definition: An angle is in standard position if

• its first side (initial side) is a ray from the origin along the positive x­axis

• its second side (terminal side) is any ray from the origin

• the angle is measured from the initial to the terminal side in a counterclockwise direction

Angle is in standard position.

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Use the coordinate definition of the trigonometric ratios to find sin , cos and tan if angle is in standard position 

• P(3, 4) is on its terminal arm

• P(-3, 4) is on its terminal arm

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Θ  sinΘ  cosΘ   tanΘ  300

1500 650 1150 890 910 

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• Find the size of each angle (nearest tenth)• State acute and obtuse angles where possible

1)  sin = 0.42

2)  cos = ­0.3

3)  tan = 1.5

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Assignment:

Exercise 18