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