How to solve limits for trigonometric sequences? \(\displaystyle\lim_{{{n}\to\infty}}{n}^{{3}}{\left({1}-{\cos{{\left({\frac{{{1}}}{{{n}}}}\right)}}}\right)}{\sin{{\left({\frac{{{1}}}{{{n}}}}\right)}}}\)

Oliver Tyler

Oliver Tyler

Answered question

2022-04-01

How to solve limits for trigonometric sequences?
limnn3(1cos(1n))sin(1n)

Answer & Explanation

Jaslyn Allison

Jaslyn Allison

Beginner2022-04-02Added 13 answers

Notice, use double angle formula: cos2A=12sin2A
limnn3(1cos(1n))sin(1n)
=limnn3(11+2sin2(12n))sin(1n)
=limnn2(sin2(12n)(12n)2)sin(1n)
=12limn(sin(12n)(12n))2limnsin(1n)(1n)
=12(1)2(1)=12

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