# Unit Circle: y-axis Symmetry

- Author:
- Whit Ford

- Topic:
- Circle, Symmetry, Unit Circle

**Symmetry in Trigonometry**

**The green slider**determines the angle

The angle is equal to .
Move the green slider to the left and right, and watch how points and are always
symmetrical to one another about the and , are symmetric about the and
Pairs of points that are symmetric about the

*y*-axis. If two points, such as*y*-axis, - How must their*x*-coordinates be related? - How must their*y*-coordinates be related? The graph above illustrates the*y*-axis symmetry displayed by the angles*y*-axis will**always**: - have*x*-coordinates that are the negative of one another - have the same*y*-coordinates Note that negative angles are displayed as their positive equivalents. If you wish to use other applets similar to this, you may find an index of all my applets here: https://mathmaine.com/2010/04/27/geogebra/