Question #592c3

1 Answer
Dec 14, 2015

When the angle between them is between #90\deg and 270\deg#

Explanation:

scalar product of two vectors is given by # \vec{a}\dot\vec{b}=|a||b|cos\theta#,where #\theta# is the angle between the two vectors. The modulus of vectors are always positive, so the only way the scalar product is negative would be if #\cos \theta# is negative, which is for #(90, 270)\deg#