InterviewSolution
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InterviewSolution
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If z = `sec^(-1) (x + 1/x) + sec^(-1) (y + 1/y)`, where xy< 0, then the possible value of z is (are)A. `(8pi)/(10)`B. `(7pi)/(10)`C. `(9pi)/(10)`D. `(21pi)/(20)` |
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Answer» Correct Answer - C::D `xy lt 0` `rArr x + (1)/(x) ge 2, y + (1)/(y) le -2` or `x + (1)/(x) le -2, y + (1)/(y) ge 2` `x + (1)/(x) ge 2` `rArr sec^(-1) (x + (1)/(x)) in [(pi)/(3), (pi)/(2))` `y + (1)/(y) le -2` `rArr sec^(-1) (y + (1)/(y)) in ((pi)/(2), (2pi)/(3)]` `rArr z in ((5pi)/(6), (7pi)/(6))` |
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