The degree of the angle is shown in figure 1 and figure 2. Through the above measurement, it is found that the route of billiards hitting the table edge forms an angle with the table edge, and the route of bouncing off also forms an angle with the table edge, and the number of the two angles is the same. According to this drawing, as shown in Figure 3 and Figure 4.

Expand:

1. Billiards is an elegant indoor sport, which is very popular in the world. It is an indoor recreation, hitting the ball on the stage with a club, and deciding the outcome of the game by calculating the score. Billiards have developed into a variety: Chinese eight-ball, Russian snooker, English snooker, Karen billiards, American snooker and snooker, among which snooker is the most common and has become a game.

2. Billiards is also called table tennis (the name of Hong Kong and Macao) and billiards (the name of Taiwan Province Province). At first billiards were made of wood, and then ivory appeared. It is said that one ivory can only make five balls. In Britain, it takes tens of thousands of elephants to make billiards. Ivory billiards must be carefully selected and have the same weight, so the price is very expensive! So ivory billiards is only suitable for court nobles to play! Later, Heath, known as the father of American plastic industry, developed a billiards made of nitrocellulose, camphor, alcohol and other chemical raw materials, which greatly reduced the cost of billiards. Then in 1920, a kind of billiards made of stone carbonate appeared, and the manufacturing cost of billiards was lower.

3. Billiards are made of synthetic resin, mainly including polyester, unsaturated polyester, phenolic resin, urea-formaldehyde resin and other varieties. The prices and grades of different materials vary greatly. The standard ball of international competition is made of phenolic resin.