Question

For two vectors A and B, what is A.B (if they have angle α between them)?

(a) |A||B| cosα

(b) |A||B|

(c) √(|A||B|) cosα

(d) |A||B| sinα

The question was posed to me in an interview.

My doubt is from Dot Product and Cross Product in section Force Vectors of Engineering Mechanics

Answer 1

Right answer is (a) |A||B| cosα

Explanation: The dot product of the two vectors is always the product of the magnitudes of the two forces and the cosine of the angle between them. We need to consider the triangle and then accordingly apply the trigonometry. This is one of the ways of resolving the components.