# Question #74c1d

##### 1 Answer

Apr 29, 2016

The angle is 45 degrees.

#### Explanation:

The sum of three vectors is zero means they form a triangle. With two equal sides, this is an iscosceles triangle. The sum of the vectors of equal magnitude by definition is aligned with the median between the first two. Thus

The third vector has a length equal to 2 cosine of the angle between it and either of the two. That angle is 45 degrees.