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Problem 11 - Entrance Test

If sin(x) = 3/5 and x is in the second quadrant, what is the value of cos(x)?

Correct: B

We know that sin^2(x) + cos^2(x) = 1. So cos^2(x) = 1 - sin^2(x) = 1 - (3/5)^2 = 1 - 9/25 = 16/25. Therefore, cos(x) = ±√(16/25) = ±4/5. Since x is in the second quadrant, cos(x) is negative. Thus, cos(x) = -4/5.