Question

find the scalar product Ā•B of the two vectors. The magnitudes of the vectors are A=4.00 and B=5.00

Answer 1

The scalar product by definition

$$({\vec A}\cdot{\vec B})=AB\cos\theta$$

So

$$({\vec A}\cdot{\vec B})=4.00\times 5.00\cos\theta$$

$$=20.0\cos\theta$$

Here theta is an angle between vectors A and B.