10.2 Find any three vectors with a zero sum such that subtracting the third vector from the sum of any two vectors results in a vector of length 1.
10.2 three vectors of length $1 / 2$, directed from the center of an equilateral triangle to its vertices.

The algebraic sum $\mathbf{a}+\mathbf{b}-\mathbf{c}$ is obtained from the zero sum of vectors a, b, and c by subtracting twice the vector c. Therefore, the length of each vector should be equal to $1 / 2$. The three vectors given in the answer satisfy these conditions.