An angle is formed by joining two rays at their starting points. The point where they are joined is called the vertex of the angle. The measure of an angle is the amount of a circle between the two rays.
An angle measured counterclockwise from the initial side has a positive measure, while an angle measured clockwise from the initial side has a negative measure.
Activity or remark - Something about the circumference of a circle being another way to measure the angle. divide both sides by the radius, so a full circle or radians