InterviewSolution
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InterviewSolution
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Sides of `DeltaABC` are in A.P. If `a lt "min" {b,c}`, then cos A may be equal toA. `(4b - 3c)/(2b)`B. `(3c -4b)/(2c)`C. `(4c -3b)/(2b)`D. `(4c -3b)/(2c)` |
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Answer» Correct Answer - A::D Sides are in A.P. and `a lt` min {b,c} Therefore, order of A.P. can be b, c, a, or c, b, a Case I : If `2c = a + b`, then `cos A = (b^(2) + c^(2) -a^(2))/(2bc) = (b^(2) + c^(2) -(2c -b)^(2))/(2bc) = (4b - 3c)/(2b)` Case II If `2b = a + c`, then `cos A = (b^(2) + c^(2) -a^(2))/(2bc) = (b^(2) + c^(2) - (2b -c)^(2))/(2bc) = (4c -3b)/(2c)` |
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