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GATE 2021 ST – Question 20

Calculus · Sequences and Series · 1 mark · Numerical answer

Find $\lim_{n\to\infty}(2^n+n2^n\sin^2(n/2))^{1/(2n-n\cos(1/n))}$.

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Correct answer: 2 to 2

Explanation

Take logarithms. The numerator becomes n ln 2+ln[1+n sin²(n/2)]. The extra log lies between 0 and ln(n+1),so divided by n it tends to zero. The denominator divided by n tends to 2−1=1. Hence the log limit is ln 2 and the original limit is **2**.

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