InterviewSolution
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InterviewSolution
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In `DeltaABC`, if `(sin A)/(c sin B) + (sin B)/(c) + (sin C)/(b) = (c)/(ab) + (b)/(ac) + (a)/(bc)`, then the value of angle A isA. `120^(@)`B. `90^(@)`C. `60^(@)`D. `30^(@)` |
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Answer» Correct Answer - B `(sinA)/(c sin B) + (sin B)/(c) + (sin C)/(b) = (c)/(ab) + (b)/(ac) + (a)/(bc)` or `(a)/(bc) + (sinB)/(c) + (sin C)/(b) = (c)/(ab) + (b)/(ab) + (a)/(bc)` or `(sin B)/(c) + (sin C)/(b) = (c)/(ab) + (b)/(ac)` or `(b sin B + c sin C)/(bc) = (c^(2) + b^(2))/(abc)` or `a = (b^(2) + c^(2))/(b sin B + c sin C)` `= (b (2R sin B) + c(2R sin C))/(b sin B + c sin C)` `= 2R` `rArr angleA = (pi)/(2)` |
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