ANGLES

          An angle is a figure formed by two rays with a common endpoint, and which are not on the same line. The two rays are called the sides of the angle. The common endpoints of the sides of an angle is called the vertex.

          In the figure above, rays OT and OX are the sides of the angle. Point O is the vertex of the angle.
          An angle is denoted using a number, vertex, or the vertex and two points on each side of an angle. If three letters are used, the middle letter is the vertex of the angle. The angle above is denoted by Angle TOX, or Angle O.
        
          An angle divides the plane into three parts: the interior angle, the exterior of the angle, and the angle itself.
          The color light blue portion outside the angle is called the exterior of the angle and the violet portion inside the angle is called the interior of the angle.


KINDS OF AN ANGLE