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reference.epsThe above figure shows four possible positions of the angle
--one in each of the four quadrants. Another angle,
, is also marked. This is sometimes called the
reference angle for . In each case,
and . Also, ,
recalling that .
The choice of depends upon the
- Quadrant I
- Quadrant II
- Quadrant III
- Quadrant IV
One mnemonic device to remember the signs of the trig functions sine,
cosine and tangent (sine/cosine) in the
four quadrants is A Smart Trig Class:
- All three trig functions are positive in Quadrant I.
- Only Sine is positive in Quadrant II; the
others are negative.
- Only Tangent is positive in Quadrant III; the others
- Only Cosine is positive in Quadrant IV; the others are
Wed Apr 21 08:17:28 EDT 1999