A quadrantal angle is an angle in angle standard position whose terminal side lies on
the x-axis or y-axis.
Equivalently, its measure is an integer multiple
of 
.
Under the usual convention, quadrantal angles have no reference
angle.
Quadrantal Angle
See also
Angle, Angle Standard Position, Nonquadrantal Angle, Reference Angle, Terminal SideExplore with Wolfram|Alpha
References
Abramson, J. "Angles." §7.1 in Algebra and Trigonometry. Houston, TX: OpenStax, 2015. https://openstax.org/books/algebra-and-trigonometry/pages/7-1-angles.Cite this as:
Weisstein, Eric W. "Quadrantal Angle." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/QuadrantalAngle.html