The black vector v is 5 units long. The right triangle formed is a 30-60-90 right triangle. Its hypotenuse is 5, the length of the black vector. The length of the short leg, the red vector, is 1/2 the hypotenuse or 5/2. It is +5/2 because it goes up. The length of the long leg, the green vector, is √3 times the short leg, which is -(5/2)√3. It is negative because it goes left. The black vector is the vector sum of the green vector plus the red vector. The green vector is i. The red vector is j So v = i + j <--ANSWER Edwin