7-4
The steps:
1. Find the Quadrant
2. Determine + or
3. Subtract 180 until b/w 0 & 90
4. Use trig chart or leave it.
Detailed Example: Find a reference anlge of cos225 degreesFirst, find the quadrant, 225 is between 180 and 270 so its in the third quadrant.Cos is related to the x axis, x is negative in the third quadrant, which makes it negativeNext, start subtracting 180 until you reach an angle between 0 and 90225-180=45 degrees, which is on the trig chart! joy!45 degrees is pi/4, take out your trig chart and look at the cos part, look for pi/4there's your answer! -squareroot of 2/2 (the negative is from the second step,it is carried)
Short Example: Find a reference angle of sin 600 degrees
1. Quadrant III
2. Negative
3. 60 degrees
4. 60 = pi/3 on trig chart
Final answer: Sin600=-sin60=square root of 3/2
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