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Evaluate the following : limx→a[sinx-sinax5-a5] - Mathematics and Statistics

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Question

Evaluate the following :

`lim_(x -> "a") [(sinx - sin"a")/(root(5)(x) - root(5)("a"))]`

Sum

Solution

`lim_(x -> "a") (sinx - sin"a")/(root(5)(x) - root(5)("a"))`

= `lim_(x -> "a") (2cos((x + "a")/2) sin((x - "a")/2))/(root(5)(x) - root(5)("a"))`

= `lim_(x -> "a") (2cos((x + "a")/2) sin((x - "a")/2)/(((x - "a")/2)))/(((root(5)(x) - root(5)("a"))/(x - "a"))) xx 1/2   ...[(because x -> "a"","  x ≠ "a"),(therefore x - "a" ≠ 0)]`

= `([lim_(x -> "a") cos((x + "a")/2)] xx [lim_(x -> "a") (sin((x - "a")/2))/(((x - "a")/2))])/(lim_(x -> "a") ((x^(1/5) - "a"^(1/5))/(x - "a"))`

= `(cos(("a" + "a")/2)*1)/(1/5"a"^(-4/5))   ...[(because x -> "a"","  x ≠ "a"  therefore (x - "a")/2 ->0),("and" lim_(theta -> 0) (sin theta)/theta = 1),("Also""," lim_(x -> "a") (x^"n" - "a"^"n")/(x - "a") = "na"^("n" - 1))]`

= `5"a"^(4/5) cos"a"`

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Substitution Method
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Chapter 7: Limits - Exercise 7.5 [Page 150]
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