मराठी

If x = ecos2t and y = esin2t, prove that dydxdydx=-ylogxxlogy

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प्रश्न

If x = ecos2t and y = esin2t, prove that `"dy"/"dx" = (-y log x)/(xlogy)`

बेरीज
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उत्तर

Given that: ecos2t and y = esin2t

⇒ cos 2t = log x and sin 2t = log y.

Differentiating both the parametric functions w.r.t. t

`"dx"/"dt" = "e"^(cos2"t") * "d"/"dt" (cos 2"t")`

= `"e"^(cos 2"t") (- sin 2"t") * "d"/"dt" (2"t")`

= `- "e"^(cos2"t") * sin 2"t" * 2`

= `2"e"^(cos2"t") * sin 2"t"`

Now y = esin2t

`"dy"/"dt" = "e"^(sin2"t") * "d"/"dt"(sin 2"t")`

= `"e"^(sin2"t") * cos 2"t" * "d"/"dt"(2"t")`

= `"e"^(sin2"t") * cos 2"t" * 2`

= `2"e"^(sin2"t") * cos 2"t"`

∴ `"dy"/"dx" = ("dy"/"dt")/("dx"/"dt")`

= `(2"e"^(sin2"t") * cos2"t")/(-2"e"^(cos2"t") * sin 2"t")`

= `("e"^(sin2"t") * cos2"t")/(-"e"^(cos2"t") * sin2"t")`

= `(y cos 2"t")/(-x sin 2"t")`

= `(y log x)/(-x log y)`   ......`[(because cos 2"t" = log x),(sin 2"t" = log y)]`

Hence, `"dy"/"dx" = - (y log x)/(x log y)`.

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पाठ 5: Continuity And Differentiability - Exercise [पृष्ठ ११०]

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एनसीईआरटी एक्झांप्लर Mathematics Exemplar [English] Class 12
पाठ 5 Continuity And Differentiability
Exercise | Q 49 | पृष्ठ ११०

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