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F(x) = k,if,if{1-coskxxsinx, if x≠012, if x=0 at x = 0 - Mathematics

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प्रश्न

f(x) = `{{:((1 - cos "k"x)/(xsinx)",",   "if"  x ≠ 0),(1/2",",  "if"  x = 0):}` at x = 0

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उत्तर

We have f(x) = `{{:((1 - cos "k"x)/(xsinx)",",   "if"  x ≠ 0),(1/2",",  "if"  x = 0):}` 

Since, f(x) is continuous at x = 0

∴ f(0) = `lim_(x -> 0) "f"(x)`

∴ `1/2 = lim_(x -> 0) (1 - cos "k"x)/(xsinx)`

= `lim_(x -> 0) (1 - cos^2"k"x)/(xsinx) * 1/(1 + cos "k"x)`

= `lim_(x -> 0) (sin^2"k"x)/(xsinx) * 1/(1 + cos"k"x)`

= `lim_(x -> 0) (((sin "k"x)/("k"x))^2 "k"^2)/((sinx)/x) * 1/(1 + cos "k"x)`

= `"k"^2/1 * 1/(1 + 1)`

= `"k"^2/2`

⇒ k2 – 1

⇒ k = ±1

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पाठ 5: Continuity And Differentiability - Exercise [पृष्ठ १०८]

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एनसीईआरटी एक्झांप्लर Mathematics [English] Class 12
पाठ 5 Continuity And Differentiability
Exercise | Q 14 | पृष्ठ १०८

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