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Angles and their Measures Essential question – What is the vocabulary we will need for trigonometry?. Trigonometry vocabulary. Initial side – start side of angle Terminal side – end side of angle Standard position – An angle whose initial side is on the positive x-axis
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Angles and their MeasuresEssential question – What is the vocabulary we will need for trigonometry?
Trigonometry vocabulary Initial side – start side of angle Terminal side – end side of angle Standard position – An angle whose initial side is on the positive x-axis Coterminal angle – Angles that have the same terminal side Reference angle – The acute angle formed by the terminal side of the given angle and the x-axis. Standard Position - An angle is in standard position if its vertex is located at the origin and one ray is on the positive x-axis.
Positive angles • Initial side on the positive x-axis and rotate counterclockwise
Negative angles • Initial side on the positive x-axis and rotate clockwise
Quadrants Quadrant II Quadrant I Quadrant III Quadrant IV
Standard PositionAn angle is in standard position if its vertex is located at the origin and one ray is on the positive x-axis. The ray on the x-axis is called the initial side and the other ray is called the terminal side.
Examples • What quadrant is the terminal side of the angle in? (Make a sketch of the angle)
Reference angles • The reference angle is the acute angle formed by the terminal side of the given angle and the x-axis. Reference angles may appear in all four quadrants. Angles in quadrant I are their own reference angles.
Examples • What are the reference angles for each of these angles?
Radians • Angle degrees can also be expressed in radians • Radians is the ratio of the length of an arc to its radius • Radians are expressed in terms of • = 180o • To change from degrees to radians, multiply by and reduce. • To change from radians to degrees, multiply by
Examples • Change from degrees to radians • Change from radians to degrees
Examples - Coterminal angles • You can add or subtract multiples of 360 or -360 to find coterminal angles • Find 2 coterminal angles (one positive and one negative) for 35o • Find 2 coterminal angles (one positive and one negative) for -23o • Find 2 coterminal angles (one positive and one negative) for 740o
Coterminal Examples using radians • Add or subtract 2π to angle