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QJEEAdv22Ma7928: JEE Advanced 2022 Mathematics - Class 12 JEEAdv22Ma7928 Solution: If then the value of is ___________.

If

β=lim⁡x→0ex3−(1−x3)13+((1−x2)12−1)sin⁡xxsin⁡2x,\beta=\lim \limits_{x \to 0} \frac{e^{x^{3}}-\left(1-x^{3}\right)^{\frac{1}{3}}+\left(\left(1-x^{2}\right)^{\frac{1}{2}}-1\right) \sin x}{x \sin ^{2} x},

then the value of 6β6 \beta is ___________.

Step-by-Step Verified Solution

Given,

β=lim⁡x→0ex3−(1−x3)13+((1−x2)12−1)sin⁡xxsin⁡2x\beta = \mathop {\lim }\limits_{x \to 0} {{{e^{{x^3}}} - {{(1 - {x^3})}^{{1 \over 3}}} + ({{(1 - {x^2})}^{{1 \over 2}}} - 1)\sin x} \over {x{{\sin }^2}x}}

=lim⁡x→0(1+x3 + ...)−(1−x33 + ...)+((1−12x2 + ...)−1)xx . sin⁡2xx2 . x2= \mathop {\lim }\limits_{x \to 0} {{(1 + {x^3}\, + \,...) - \left( {1 - {{{x^3}} \over 3}\, + \,...} \right) + \left( {\left( {1 - {1 \over 2}{x^2}\, + \,...} \right) - 1} \right)x} \over {x\,.\,{{{{\sin }^2}x} \over {{x^2}}}\,.\,{x^2}}}

=lim⁡x→0(x3+x33−x32)+x4(......)x3= \mathop {\lim }\limits_{x \to 0} {{\left( {{x^3} + {{{x^3}} \over 3} - {{{x^3}} \over 2}} \right) + {x^4}(......)} \over {{x^3}}}

=lim⁡x→0x3(1+13−12)x3= \mathop {\lim }\limits_{x \to 0} {{{x^3}\left( {1 + {1 \over 3} - {1 \over 2}} \right)} \over {{x^3}}} [Neglecting higher power of x]

=1+13−12=56= 1 + {1 \over 3} - {1 \over 2} = {5 \over 6}

∴\therefore 6β=6×56=56\beta = 6 \times {5 \over 6} = 5

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