When guiding students to do this kind of problems, they will first make it clear that the characteristics of an angle are composed of a vertex and two straight sides. When calculating angles, we should judge which angles are according to the characteristics of angles (first find a vertex, and then see if the two sides drawn from this vertex are straight), and then calculate the number of angles. When there are multiple angles in the picture, in order to avoid repetition or omission, the angles should be counted in a certain order. Count the basic angles first, and then the constituent angles.
1, when we count angles, we only need to count the internal angles of the graph, not the external angles. For example, a triangle has three corners, and a hexagon has six corners.
2. If it is a combination angle of multiple sides, only the number of angles formed by two adjacent sides needs to be counted.
If you can count two, three or four adjacent corners, you should give students affirmation and great encouragement.
4. If there is only one vertex, counting the outermost two rays and there are n rays in a * * *, then the number of total * * angles is1+2+3+...+(n-2)+(n-1).