Complete the sentences according to the text:

1. To simplify the equations, Willard Gibbs introduced … .
2. Usually, bold face symbols (F, a) stand for … .
3. The symbol |A| or simply A indicates … .
4. According to geometrical definition, a vector is … .
5. In physics, vectors can describe … .
6. To add two vectors, we have to … .
7. To subtract two vectors, we have to … .
8. The scalar product is an operation that … .
9. The vector product is an operation, in which … .
10. 10. The concept of a displacement vector differs in physics and mathematics. In mathematics …. whereas in physics … .