In trigonometry an angle is usually drawn in what is called the "standard position" as shown below.
In this position, the vertex of the angle (B) is on the origin of the x and y axis. One side of the angle
is always fixed along the positive x-axis - that is, going to the right along the axis in the 3 o'clock direction (line BC).
This is called the initial side of the angle.
The other side of the angle is called the terminal side.
While you are here..
... I have a small favor to ask. Over the years we have used advertising to support the site so it can remain free for everyone.
However, advertising revenue is falling and I have always hated the ads. So, would you go to Patreon and become a patron of the site?
When we reach the goal I will remove all advertising from the site.
It only takes a minute and any amount would be greatly appreciated.
Thank you for considering it! – John Page
Become a patron of the site at patreon.com/mathopenref
(C) 2011 Copyright Math Open Reference. All rights reserved