If in a triangle ABC, b + c 11 = c + a 12 = a + b 13 , then cos A is equal to

JEE Main 2012 Mathematics question

Not in JEE syllabus

If in a triangle ABC, , then cos A is equal to

Answer: (2)

Let the common value be k: a + b + c = 18k, so a = 7k, b = 6k, c = 5k. $ A

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Question ID VK-103516