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MHT CET202617 April 2026Morning ShiftMathematicsProperties of TrianglesActual

In ABC , if a = 13, b = 14, c = 15 , then the value of A + A is...

Options

  1. A3 5
  2. B7 5
  3. C4 5
  4. D12 5

Correct answer

B. 7 5

Step-by-step solution

Using the cosine rule in ABC : A = b^2 + c^2 - a^2 2bc Substituting the given values a = 13 , b = 14 , c = 15 : A = 14^2 + 15^2 - 13^2 2 14 15 A = 196 + 225 - 169 420 A = 252 420 = 3 5 Since A is an angle of a triangle, A > 0 . A = 1 - ^2 A = 1 - ( 3 5 )^2 = 4 5 Therefore, A + A = 4 5 + 3 5 = 7 5 Answer: 7 5

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