Static: An angle is a graph composed of two rays with a common endpoint, and the common endpoint of the two rays is the vertex of the angle. An angle is usually represented by three letters and the symbol "∞". It can also be represented by numbers or letters (provided that the vertex has only one angle). Dynamically: An angle can also be regarded as a ray rotating around its endpoint. A ray rotates around its endpoint. When the starting edge and the ending edge are in a straight line, the angle obtained is called a straight angle. The ending edge continues to rotate, and the angle obtained when it coincides with the starting edge is called fillet. Please give it to me.