Medium MCQ +4 / -1 PYQ · JEE Mains 2022

The value of $$\mathop {\lim }\limits_{x \to 1} {{({x^2} - 1){{\sin }^2}(\pi x)} \over {{x^4} - 2{x^3} + 2x - 1}}$$ is equal to:

  1. A ${{{\pi ^2}} \over 6}$
  2. B ${{{\pi ^2}} \over 3}$
  3. C ${{{\pi ^2}} \over 2}$
  4. D $\pi$<sup>2</sup> Correct answer

Solution

<p>$$\mathop {\lim }\limits_{x \to 1} {{({x^2} - 1){{\sin }^2}(\pi x)} \over {{x^4} - 2{x^2} + 2x - 1}}$$</p> <p>$$ = \mathop {\lim }\limits_{x \to 1} {{({x^2} - 1)si{n^2}(\pi x)} \over {({x^2} - 1){{(x - 1)}^2}}}$$</p> <p>$= \mathop {\lim }\limits_{x \to 1} {{{{\sin }^2}(\pi x)} \over {{{(x - 1)}^2}}}$</p> <p>Let $x = 1 + h$</p> <p>$\therefore$ when x $\to$ 1 then h $\to$ 0</p> <p>$$ = \mathop {\lim }\limits_{h \to 0} {{{{\sin }^2}(\pi (1 + h))} \over {{{(1 + h - 1)}^2}}}$$</p> <p>$= \mathop {\lim }\limits_{h \to 0} {{{{\sin }^2}(\pi h)} \over {{h^2}}}$</p> <p>$$ = \mathop {\lim }\limits_{h \to 0} {\pi ^2} \times {{{{\sin }^2}(\pi h)} \over {{{(\pi h)}^2}}}$$</p> <p>$= {\pi ^2} \times 1$</p> <p>$= {\pi ^2}$</p>

About this question

Subject: Mathematics · Chapter: Limits, Continuity and Differentiability · Topic: Limits and Standard Results

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