1. Static: An angle is a graph composed of two rays at a common * * * endpoint. These two rays are called the edges of an angle, and their common endpoint is called the vertex of the angle.

2. Dynamic: An angle can also be regarded as a graph formed by a ray rotating around its endpoint from its starting position to its ending position. The starting position of the ray is called the starting edge of the angle, and the ending position is called the ending edge of the angle.

These are 9. 1 in the seventh grade of Qingdao textbook.

There are two sentences in the second paragraph on page four and the third paragraph on page five.

I hope these can help you.