a vector points in north west direction.the negative of this vector will point in which direction

Answer 1

For this kind of a problem always draw a picture.

In this case, you need to understand the convention for naming compass coordinates---and the relationship to degrees. The basic "points" of the compass, and the number of degrees(clockwise) from North:

N: 0

E: 90

S: 180

W: 270

By convention, "NorthWest" means 1/2 way between North and West. This is a bearing of 315 degrees, which is 45 degrees west of North. The opposite vector is 1/2 way between East and South, at a bearing of 135 degrees. The is called "Southeast".

Working strictly in degrees, we get the opposite of a vector by adding or subtracting 180 degrees.