Trigonometrical Equations 2 Question 1

1. All x satisfying the inequality (cot1x)27(cot1x)+10>0, lie in the interval

(2019 Main, 11 Jan II)

(a) (,cot5)(cot2,)

(b) (cot5,cot4)

(c) (cot2,)

(d) (,cot5)(cot4,cot2)

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Answer:

Correct Answer: 1. (c)

Solution:

  1. Given, (cot1x)27(cot1x)+10>0 (cot1x2)(cot1x5)>0 cot1x<2 or cot1x>5

(by factorisation)

By wavy curve method,

cot1x(,2)(5,) cot1x(0,2)[ Range of cot1x is (0,π)]

x(cot2,)



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