A1260717369YwuZD

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Trigonometry L1-3 Measure of Rotation
An angle is in standard position if
1. Its initial side is along the positive
x-axis. (Always start on the x-axis!!!)
2. Its vertex is at the origin.
3. It rotates counterclockwise if its
positive. clockwise if its negative.
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Coterminal Angles are angles whose terminal side
is the same.
i.e. 0º, 360º or -45º, 315º
Reference Angles are angles that fall between the
x-axis and the terminal side.
i.e. 135º has a reference angle of 45º.
135º
45º
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Rules for Reference Angles
If ? is in Q1, reference ?
If ? is in Q2, reference 180º - ?
If ? is in Q3, reference ? - 180º
If ? is in Q4, reference 360º - ?
?
?
?
reference
reference
reference
reference
?
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NOTE For negative angles, ignore signs and use
the rules backwards
Ex1. Sketch ? -220º and find its reference
217º
40º
37º
-220º
Ex2. Sketch ? 4897º and find its reference
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Converting minutes to degrees
There are 60 minutes in a degree.
Ex3. Convert ? 15437 to degrees
? 154.617