Answer: 2F cos(theta/2).
- A 2F
- B F cos(theta)
- C F sin(theta)
- D 2F cos(theta/2)
Correct answer: D. 2F cos(theta/2)
Explanation: |R|<sup>2</sup> = F<sup>2</sup>+F<sup>2</sup>+2F<sup>2</sup> cos(theta) = 2F<sup>2</sup>(1+cos(theta)) = 4F<sup>2</sup> cos<sup>2</sup>(theta/2). So |R| = 2F cos(theta/2).
Triangle law of vector addition: placing vector b at the head of vector a, the diagonal from the start to the final head gives the resultant a + b.
Concept context
Vectors, dot product, cross product, and geometric applications