I would like to know why the answer is right btw.

what is your answer

Ask yourself what the definition of a dot product is

You know that a dot product for a vector A and B is:

A*B = |A|*|B|*Cos(angle)

where |A| and |B| are norms of the two vectors

keep in mind that since they are both parallel, the angle between both is 0

cos(0) = 1

therefore

V1*V2 = |V1|*|V2|*cos(0)
V1*V2 = |V1|*|V2|

That makes a lot of sense...so, if the angle is perpendicular, do I just put 90 in cos(x) = 0?

Yes, perpendicular vectors have a dot product equal to zero.

Thumb rules:
1. For parallel vectors, cross product is 0, dot product is the direct multiplication of the two magnitudes.
2. For perpendicular vectors, dot product is 0, cross product is the direct multiplication of the two magnitudes.

You could always be a smart ass and say always 0, since they never said V1 or V2 couldn't be the zero vector.

But yes, the above is correct.

This post was edited by Casey on Aug 25 2014 04:09am

dont listen to this guy

leb is right

don't listen to this guy

but leb is right

I like your thinking