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(i) \newlinelimx0(tan2xsin2xx3) \lim_{x \to 0} \left( \frac{\tan 2x - \sin 2x}{x^{3}} \right)

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Q. (i) \newlinelimx0(tan2xsin2xx3) \lim_{x \to 0} \left( \frac{\tan 2x - \sin 2x}{x^{3}} \right)
  1. Recognize Limit Problem: Recognize the limit problem and apply L'Hôpital's Rule if necessary.\newlineSince the limit is of the form 0/00/0, we can apply L'Hôpital's Rule, which states that if the limit of f(x)/g(x)f(x)/g(x) as xx approaches a value cc is of the form 0/00/0 or ±/±\pm\infty/\pm\infty, then the limit is the same as the limit of f(x)/g(x)f'(x)/g'(x) as xx approaches cc, provided that this latter limit exists.
  2. Differentiate Numerator and Denominator: Differentiate the numerator and denominator separately.\newlineThe derivative of the numerator tan(2x)sin(2x)\tan(2x) - \sin(2x) with respect to xx is sec2(2x)2cos(2x)2\sec^2(2x)\cdot 2 - \cos(2x)\cdot 2.\newlineThe derivative of the denominator x3x^3 with respect to xx is 3x23x^2.
  3. Apply L'Hôpital's Rule Once: Apply L'Hôpital's Rule once.\newlineWe now have the new limit as xx approaches 00 of (2sec2(2x)2cos(2x))/(3x2)(2\cdot\sec^2(2x) - 2\cdot\cos(2x)) / (3x^2).
  4. Evaluate New Limit: Evaluate the new limit as xx approaches 00. As xx approaches 00, sec2(2x)\sec^2(2x) approaches sec2(0)\sec^2(0) which is 11, and cos(2x)\cos(2x) approaches cos(0)\cos(0) which is also 11. So, the limit becomes 0000 which simplifies to 0011, indicating that we need to apply L'Hôpital's Rule again.
  5. Differentiate Again: Differentiate the new numerator and denominator again.\newlineThe derivative of the new numerator 2sec2(2x)2cos(2x)2\sec^2(2x) - 2\cos(2x) with respect to xx is 22sec2(2x)tan(2x)22(sin(2x)2)2\cdot2\cdot\sec^2(2x)\cdot\tan(2x)\cdot2 - 2\cdot(-\sin(2x)\cdot2).\newlineThe derivative of the new denominator 3x23x^2 with respect to xx is 6x6x.
  6. Apply L'Hôpital's Rule Second Time: Apply L'Hôpital's Rule a second time.\newlineWe now have the new limit as xx approaches 00 of (8sec2(2x)tan(2x)4sin(2x))/6x(8\cdot\sec^2(2x)\cdot\tan(2x) - 4\cdot\sin(2x)) / 6x.
  7. Evaluate New Limit: Evaluate the new limit as xx approaches 00. As xx approaches 00, sec2(2x)\sec^2(2x) approaches 11, tan(2x)\tan(2x) approaches 00, and sin(2x)\sin(2x) approaches 00. So, the limit becomes 0000 which simplifies to 0011, indicating that we need to apply L'Hôpital's Rule yet again.
  8. Differentiate Again: Differentiate the new numerator and denominator again.\newlineThe derivative of the new numerator 8sec2(2x)tan(2x)4sin(2x)8\sec^2(2x)\tan(2x) - 4\sin(2x) with respect to xx is 8(2sec2(2x)tan(2x)2+2sec2(2x)sec2(2x)2)4(cos(2x)2)8\left(2\sec^2(2x)\tan(2x)\cdot 2 + 2\sec^2(2x)\sec^2(2x)\cdot 2\right) - 4\left(\cos(2x)\cdot 2\right).\newlineThe derivative of the new denominator 6x6x with respect to xx is 66.
  9. Evaluate New Limit: Evaluate the new limit as xx approaches 00. As xx approaches 00, sec2(2x)\sec^2(2x) approaches 11, tan(2x)\tan(2x) approaches 00, and cos(2x)\cos(2x) approaches 11. So, the limit becomes 0000 which simplifies to 0011 which further simplifies to 0022.
  10. Simplify Final Answer: Simplify the result to find the final answer.\newlineThe final answer is (168)/6(16 - 8) / 6 which simplifies to 8/68 / 6, and further simplifies to 4/34 / 3.

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