Hints

1. What are the x  and y components of the blue vector?
2. What are the x and y components of the red vector?
3. Drag the tail of the red vector so that it is on top of the blue vector's head.
4. The vector sum is now a vector that reaches from the tail of the first (blue) vector to the head of the second (red) vector.
5. What are the components of this vector sum?
6. How do they relate to the components of the original (blue and red) vectors?

Reference

See Walker, Section 3-3

Illustration written by Steve Mellema and Chuck Niederriter