If the magnitude of the resultant of two equal vectors is equal to the magnitude of either vector, what is the angle between them?
Q1. If the magnitude of the resultant of two equal vectors is equal to the magnitude of either vector, what is the angle between them?
Answer: 120 degrees
Explanation: If R=A=B, the law of cosines R^2 = A^2 + B^2 + 2AB cosθ requires cosθ = -1/2. Option A is for perpendicular vectors.