Final answer:
The expression to fill in the blank for step 3 is cos(A)cos(B), which aligns with the process of vector addition and calculating the angle between two vectors using the dot product and trigonometric functions.
Step-by-step explanation:
To complete step 3 in the process of vector addition and resolving the angle between two vectors, you will need to understand the concepts of the dot product and trigonometric functions. The dot product (also known as the scalar product) of two vectors is given by the equation ·B = Ax Bx + Ay By + Az Bz, and the cosine of the angle p between them can be found by dividing this expression by the product of the magnitudes of the vectors A and B, and taking the inverse cosine of the resulting value.
Given the options provided and the context of the question addressing vector components and angles, we must consider the trigonometric identities and vector equations involved. In this case, the expression to fill in the blank space for step 3 would be cos(A)cos(B) (Option A), as this expression aligns with the concept of obtaining the scalar components of vectors and the angle between them.