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Problem 12 - Entrance Test

If sin (A + B) = 1 and cos (A - B) = √3/2, where A and B are acute angles, then find A and B.

Correct: A

From sin (A + B) = 1, we know that sin 90° = 1. So, A + B = 90° --- (Equation 1). From cos (A - B) = √3/2, we know that cos 30° = √3/2. So, A - B = 30° --- (Equation 2). Add Equation 1 and Equation 2: (A + B) + (A - B) = 90° + 30° 2A = 120° A = 60°. Substitute A = 60° into Equation 1: 60° + B = 90° B = 90° - 60° B = 30°. Thus, A = 60° and B = 30°.