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COMEDK2012MathematicsProperties of Triangles

If b+c 11 = c+a 12 = a+b 13 , then A is equal to

Options

  1. A5 7
  2. B1 5
  3. C2 5
  4. D1 7

Correct answer

B. 1 5

Step-by-step solution

Let b+c 11 = c+a 12 = a+b 13 =k b+c=11 k, c+a=12 k, a+b=13 k Now, 2(a+b+c)=36 ka+b+c=18 k So, a=7 kb=6 k and c=5 k Now, A= b²+c²-a² 2 b c = 36 k²+25 k²-49 k² 2 (30 k² ) = 12 k² 60 k² = 1 5

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