Maths-
General
Easy

Question

L t subscript left parenthesis x rightwards arrow pi divided by 2 right parenthesis left square bracket s e c invisible function application 3 x c o s invisible function application 5 x right square bracket

  1. left parenthesis negative 5 right parenthesis divided by 3
  2. 5 divided by 3
  3. 3 divided by 5
  4. left parenthesis negative 3 right parenthesis divided by 5

hintHint:

We are given a function to find a limit. Before substituting the value of the limit, we should make sure we don’t get zero value.

The correct answer is: left parenthesis negative 5 right parenthesis divided by 3


    The given function is
    limit as x rightwards arrow pi over 2 of s e c 3 x cos 5 x space equals stack lim space space with x rightwards arrow pi over 2 below fraction numerator c o s 5 x over denominator cos 3 x end fraction
space space space space space space space space space space space space space space space space space space space space space space
W h e n space p u t space t h e space v a l u e space o f space x rightwards arrow pi over 2
T h e n space t h e space f u n c t i o n space i s space 0 over 0
S o comma space w e space w i l l space u s e space L apostrophe H o s p i t a l space R u l e s
space space space space space space limit as x rightwards arrow straight pi over 2 of fraction numerator f left parenthesis x right parenthesis over denominator g left parenthesis x right parenthesis end fraction space equals limit as x rightwards arrow straight pi over 2 of fraction numerator f apostrophe left parenthesis x right parenthesis over denominator g apostrophe left parenthesis x right parenthesis end fraction
space
    limit as x rightwards arrow pi over 2 of f left parenthesis x right parenthesis space equals limit as x rightwards arrow straight pi over 2 of fraction numerator 5 sin 5 x over denominator 3 sin 3 x end fraction
space space space space space space space space space space space space space space
space space space space space space space space space space space space space space space space space space space space space space space space space space equals space fraction numerator 5 sin 5 begin display style straight pi over 2 end style over denominator 3 sin 3 begin display style straight pi over 2 end style end fraction space space space space space space space

space N o w comma space space sin fraction numerator 5 straight pi over denominator 2 end fraction equals sin left parenthesis 2 straight pi plus straight pi over 2 right parenthesis space space space space space space
space space space space space space space space space space space space space space space space space space space space space space space space space equals sin straight pi over 2 space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space
space space space space space space space space space space space space space space space space space space space space space space space space equals space 1
space space space space space space space space space space space space space sin fraction numerator 3 straight pi over denominator 2 end fraction space equals space sin left parenthesis straight pi space plus space straight pi over 2 right parenthesis
space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals sin straight pi over 2
space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals 1
    limit as x rightwards arrow pi over 2 of f open parentheses x close parentheses equals fraction numerator 5 open parentheses 1 close parentheses over denominator 3 open parentheses 1 close parentheses end fraction equals 5 over 3
    This is the final answer.

    For such questions, we should know different formulas of limits. We should know L'Hospitals rule to solve question.

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