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Scalars and vectors: addition, subtraction, resolution, unit vector

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If the magnitude of sum of two vectors is equal to the magnitude of difference of the two vectors, the angle between these vectors is : Answer: 2. 90^° Key idea: |vec A+vec B|²=A²+B²+2ABcosθ and |vec A-vec B|²=A²+B²-2ABcosθ . Setting them equal gives 4ABcosθ=0 , so cosθ=0 and... Scalars and vectors: addition, subtraction, resolution, unit vector 1 answer