Associated with every angle drawn in standard position (except quadrantal angles) there is another angle called the reference angle. Basically, any angle on the x-y plane has a reference angle, which is always between 0° and 90° or 0 and π/2. The [b]reference angle[/b] is always the [b][color=#c51414]smallest angle[/color][/b] that you can make from the terminal side of an angle (ie where the angle ends) with the x-axis. A reference angle always uses the x-axis as its frame of reference. Angles in quadrant I are their own reference angles. ([url=http://www.mathwarehouse.com/trigonometry/reference-angle/finding-reference-angle.php]Ref.[/url])[br][br]Grab point [color=#c51414]A[/color], the large [color=#c51414]red point[/color], and drag it around the circle. You should note the [color=#0a971e]reference angle marked in green[/color]. Also, observe the signs of the sine and cosine.[br][br]Remember: The reference angle is measured from the terminal side of the original angle "to" the [b]x-axis[/b] (not the y-axis).[br][br]See [url=http://www.analyzemath.com/Angle/reference_angle.html]Analyze Math Reference Angle[/url] for questions.

Do cos θ and sin θ have a maximum value? [br][br]In which quadrants is cos θ negative? positive? [br][br]In which quadrants is sin θ negative? positive?