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If in triangle ABC, a, c and angle A are given and `c sin A lt a lt c`, then (`b_(1) and b_(2)` are values of b)A. `b_(1) + b_(2) = 2c cos A`B. `b_(1) + b_(2) = c cos A`C. `b_(1) b_(2) = c^(2) -a^(2)`D. `b_(1) b_(2) = c^(2) + a^(2)` |
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Answer» Correct Answer - A::C From the cosine formula, `cos A = (b^(2) + c^(2) -a^(2))/(2bc)` or `b^(2) - (2c cos A) b + (c^(2) -a^(2)) = 0`, Which is a quadratic equation in b. Therefore, `c sin A lt a lt` Therefore, two triangle will be obtained, But this is possible when two values of the thired side are also obtained. Clearly, two values of sides b will be `b_(1) and b_(2)`. Let these be the roots of the above equation. then, Sum of roots `= b_(1) + b_(2) = 2c cos A and b_(1) b_(2) = c^(2) - a^(2)` |
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