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The magnitudes of vectors A, B and C are 3, 4 and 5 units respectively. If A + B = C, then the angle between A and B is

1. π/2
2. cos⁻¹ 0.6
3. tan⁻¹ 7/5
4. π/4

Correct answer: cos⁻¹ 0.6

Solution

Using the triangle law of vector addition, if A + B = C, then the magnitudes must satisfy the Pythagorean theorem: A² + B² = C². Substituting the given magnitudes, 3² + 4² = 5², which holds true. This implies that the angle between A and B is cos⁻¹(3/5) = cos⁻¹(0.6).

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