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The general solution of ex cosy dx – ex siny dy = 0 is ______.

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Question

The general solution of ex cosy dx – ex siny dy = 0 is ______.

Options

  • ex cosy = k

  • ex siny = k

  • ex = k cosy

  • ex = k siny

MCQ
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Solution

The general solution of ex cosy dx – ex siny dy = 0 is ex cosy = k.

Explanation:

The given differential equation is ex cosy dx – ex siny dy = 0

⇒ ex (cosy dx – siny dy) = 0

⇒ cosy dx – siny dy = 0   ......[∵ ex ≠ 0]

⇒ siny dy = cosy dx

⇒ `siny/cosy "d"y` = dx

Integrating both sides, we have

`int siny/cosy "d"y = int "d"x`

⇒ `-log|cosy| = x + log "k"`

⇒ `log  1/cosy - log "k"` = x

⇒ `log(1/("k" cosy))` = x

⇒ `1/("k" cosy)` = ex

⇒ `1/"k"` = ex cosy

⇒  ex cosy = c  .....`["c" = 1/"k"]`

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Chapter 9: Differential Equations - Exercise [Page 197]

APPEARS IN

NCERT Exemplar Mathematics Exemplar [English] Class 12
Chapter 9 Differential Equations
Exercise | Q 50 | Page 197

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