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The number of real roots of the equation $${\tan ^{ - 1}}\sqrt {x(x + 1)} + {\sin ^{ - 1}}\sqrt {{x^2} + x + 1} = {\pi \over 4}$$ is :

JEE · Math · previous-year question

  1. A.1
  2. B.2
  3. C.4
  4. D.0correct

Answer

D. 0

Explanation

$${\tan ^{ - 1}}\sqrt {x(x + 1)} + {\sin ^{ - 1}}\sqrt {{x^2} + x + 1} = {\pi \over 4}$$ For equation to be defined, x2 + x $$\ge$$ 0 $$\Rightarrow$$ x2 + x + 1 $$\ge$$ 1 $$\therefore$$ Only possibility that the equation is defined x2 + x = 0 $$\Rightarrow$$ x = 0; x = $$-$$1 None of these values satisfy $$\therefore$$ No of roots = 0

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