What is the angle between \(a = (3i - 4j)\) and \(b = (6i + 4j)\)?

What is the angle between \(a = (3i - 4j)\) and \(b = (6i + 4j)\)?

A 13Â°
B 87Â°
C 100Â°
D 110Â°

waec 2010 furthermathematics

The correct answer is B. 87Â°

No explanation given

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