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Evaluate the following : limx→π6[cosx-3sinxπ-6x] - Mathematics and Statistics

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प्रश्न

Evaluate the following :

`lim_(x -> pi/6) [(cos x - sqrt(3) sinx)/(pi - 6x)]`

योग

उत्तर

Put x = `pi/6 + "h"`. Then as `x -> pi/6, "h" -> 0`.

Also, π – 6x = `pi - 6(pi/6 + "h")` = π – π – 6h = – 6h

and `cos x - sqrt(3) sinx = cos  (pi/6 + "h") - sqrt(3) sin (pi/6 + "h")` 

= `(cos  pi/6 cos "h" - sin  pi/6 sin "h") - sqrt(3) (sin  pi/6 cos "h" + cos  pi/6 sin "h")`

= `((sqrt(3))/2 cos "h" - 1/2 sin "h") - sqrt(3) (1/2  cos "h" + sqrt(3)/2 sin "h")`

= `sqrt(3)/2 cos "h" - 1/2 sin "h" - sqrt(3)/2 cos "h"  -3/2 sin "h"`

= – 2 sin h

∴ `lim_(x -> pi/6) (cos x - sqrt(3) sinx)/(pi - 6x)`

= `lim_("h" -> 0) (-2 sin "h")/(-6"h")`

= `1/3 lim_("h" -> 0) sin "h"/"h"`

= `1/3 xx 1`

= `1/3`

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Substitution Method
  क्या इस प्रश्न या उत्तर में कोई त्रुटि है?
अध्याय 7: Limits - Exercise 7.5 [पृष्ठ १५०]

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