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In triangle ABC, a = 6, b = 4 and c = 5. What is cos A?
A1/8
B1/4
C3/8
D1/2
Answer & Solution
Correct answer: A. 1/8
cos A = (b² + c² − a²)/(2bc) = (16 + 25 − 36)/40 = 1/8.
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