Angle instandard position and reference angles

Topic:
Angles
Angle instandard position and reference angles: The reference angle is the acute angle formed by the terminal side of the given angle and the x-axis. Reference angles may appear in all four quadrants. The refernce angle is measured from the terminal side of original angle TO the x-axis, not the y-axis. Angles in quadrant I are their own reference angles. Now, move the slider and see the location of reference angle.
Vera Hu-Hyneman SCCC selden, NY