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Limit Evaluation of Exponential and Algebraic Functions

If

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

then the value of 6β6\beta is ________.

Official Numerical Answer5

Step-by-Step Solution

To find the value of 6β6\beta, we first evaluate the given limit: β=lim⁡x→0ex3−(1−x3)13+((1−x2)12−1)sin⁡xxsin⁡2x\beta = \lim_{x \to 0} \frac{e^{x^3} - (1 - x^3)^{\frac{1}{3}} + \left((1 - x^2)^{\frac{1}{2}} - 1\right) \sin x}{x \sin^2 x}

We use the Taylor series expansions near x=0x = 0 for each component of the expression up to the x3x^3 term:

  1. Expansion of ex3e^{x^3}: ex3=1+x3+O(x6)e^{x^3} = 1 + x^3 + O(x^6)

  2. Expansion of (1−x3)13(1 - x^3)^{\frac{1}{3}}: (1−x3)13=1−13x3+O(x6)(1 - x^3)^{\frac{1}{3}} = 1 - \frac{1}{3}x^3 + O(x^6)

  3. Expansion of ((1−x2)12−1)sin⁡x\left((1 - x^2)^{\frac{1}{2}} - 1\right) \sin x: (1−x2)12=1−12x2+O(x4)(1 - x^2)^{\frac{1}{2}} = 1 - \frac{1}{2}x^2 + O(x^4) (1−x2)12−1=−12x2+O(x4)(1 - x^2)^{\frac{1}{2}} - 1 = -\frac{1}{2}x^2 + O(x^4) Since sin⁡x=x−x36+O(x5)\sin x = x - \frac{x^3}{6} + O(x^5), we have: ((1−x2)12−1)sin⁡x=(−12x2+O(x4))(x+O(x3))=−12x3+O(x5)\left((1 - x^2)^{\frac{1}{2}} - 1\right) \sin x = \left(-\frac{1}{2}x^2 + O(x^4)\right)\left(x + O(x^3)\right) = -\frac{1}{2}x^3 + O(x^5)

Now, substitute these expansions into the numerator: Numerator=(1+x3)−(1−13x3)−12x3+O(x5)\text{Numerator} = \left(1 + x^3\right) - \left(1 - \frac{1}{3}x^3\right) - \frac{1}{2}x^3 + O(x^5) Numerator=(1−1)+(1+13−12)x3+O(x5)\text{Numerator} = \left(1 - 1\right) + \left(1 + \frac{1}{3} - \frac{1}{2}\right)x^3 + O(x^5) Numerator=(6+2−36)x3+O(x5)=56x3+O(x5)\text{Numerator} = \left(\frac{6 + 2 - 3}{6}\right)x^3 + O(x^5) = \frac{5}{6}x^3 + O(x^5)

For the denominator, as x→0x \to 0: xsin⁡2x=x(x+O(x3))2=x3+O(x5)x \sin^2 x = x \left(x + O(x^3)\right)^2 = x^3 + O(x^5)

Substituting the numerator and denominator back into the limit: β=lim⁡x→056x3+O(x5)x3+O(x5)=lim⁡x→056+O(x2)1+O(x2)=56\beta = \lim_{x \to 0} \frac{\frac{5}{6}x^3 + O(x^5)}{x^3 + O(x^5)} = \lim_{x \to 0} \frac{\frac{5}{6} + O(x^2)}{1 + O(x^2)} = \frac{5}{6}

Thus, the value of 6β6\beta is: 6β=6×56=56\beta = 6 \times \frac{5}{6} = 5

Limit Evaluation of Exponential and Algebraic Functions | Mathematics PYQ Solution - JEE Challenger