http://www.ck12.org Chapter 5. Trigonometric Functions
measure the angle from the positive portion of thex-axis.
Knowing the first quadrant well is the key to knowing the entire unit circle. Every other point on the unit circle can
be found using logic and this quadrant.
Example A
Use your knowledge of the first quadrant of the unit circle to identify the angles and important points of the second
quadrant.
Solution: The heights are mirrored and equal which correspond to theyvalues. Thexvalues are all negative.