MCQ
$\mathop {{\rm{lim}}}\limits_{x \to 0} \frac{{{\rm{sin}}\left( {\pi {{\cos }^2}x} \right)}}{{{x^2}}} = $
  • A
    $ - \pi $
  • $\;\pi $
  • C
    $\frac{\pi }{2}$
  • D
    $1$

Answer

Correct option: B.
$\;\pi $
b
$\mathop {lim}\limits_{x \to 0} \frac{{\sin \left( {\pi {{\cos }^2}x} \right)}}{{{x^2}}}$

$ = \mathop {lim}\limits_{x \to 0} \frac{{\sin \left( {\pi \left( {1 - {{\sin }^2}x} \right)} \right)}}{{{x^2}}}$

$ = \mathop {lim}\limits_{x \to 0} \frac{{\sin \left( {\pi {{\sin }^2}x} \right)}}{{{x^2}}}$

$ = \mathop {lim}\limits_{x \to 0} \frac{{\sin \left( {\pi {{\sin }^2}x} \right)}}{{{x^2}}}$

$ = \mathop {lim}\limits_{x \to 0} \frac{{\sin \left( {\pi {{\sin }^2}x} \right)}}{{\pi {{\sin }^2}x}} \cdot \frac{{\pi {{\sin }^2}x}}{{{x^2}}}$

We know,  $\mathop {lim}\limits_{x \to 0} \frac{{\sin \left( {f\left( x \right)} \right)}}{{f\left( x \right)}} = 1$

So, our limits becomes,

$ = 1 \cdot \pi \left( 1 \right) = \pi $

$\therefore \mathop {lim}\limits_{x \to 0} \frac{{\sin \left( {\pi {{\cos }^2}x} \right)}}{{{x^2}}} = \pi $

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