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Solution of ddxdydx=y+xtan yx is sin(yx) = cx

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Question

Solution of `x("d"y)/("d"x) = y + x tan  y/x` is `sin(y/x)` = cx

Options

  • True

  • False

MCQ
True or False
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Solution

This statement is True.

Explanation:

The given differential equation is `x("d"y)/("d"x) = y + x tan (y/x)`

`x ("d"y)/("d"x) = -x tan (y/x)` = y

⇒ `("d"y)/("d"x) - tan (y/x) = y/x`

⇒ `("d"y)/("d"x) = y/x + tan (y/x)`

Put y = vx

⇒ `("d"y)/("d"x) = "v" + x "dv"/"dx"`

⇒ `"v" + x * "dv"/"dx" = "vx"/x + tan ("vx"/x)`

⇒ `"v" + x "dv"/"dx" = "v" + tan "v"`

⇒ `x "dv"/"dx" = tan "v"`

⇒ `"dv"/tan"v" = ("d"x)/x`

⇒ `cot "v" "dv" = ("d"x)/x`

Integrating both sides, we get

`int cot "v" "dv" = int ("d"x)/x`

⇒ `log sin "v" = log x + log "c"`

⇒ `log sin "v" - log x = log "c"`

⇒ `log sin  y/x = log x"c"`

∴ `sin  y/x` = xc

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Chapter 9: Differential Equations - Exercise [Page 203]

APPEARS IN

NCERT Exemplar Mathematics Exemplar [English] Class 12
Chapter 9 Differential Equations
Exercise | Q 77.(x) | Page 203

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