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CUET · MATHS · PYQ PAPER 2023

Solution of differential equation \(\frac{d y}{d x}=\cos (x+y+3)\) is:

  1. A \(y=-\sin (x+y+3)+c\)
  2. B \(y=\sin (x+y+3)+c\)
  3. C \(y=2 \tan ^{-1}(x+c)-x-3\)
  4. D \(y=\frac{1}{2} \tan ^{-1}(x+c)+x+3\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(y=2 \tan ^{-1}(x+c)-x-3\)

Step-by-step Solution

Detailed explanation

\(v = x+y+3 \implies \frac{dv}{dx} = 1 + \frac{dy}{dx}\) \(\frac{dv}{dx} - 1 = \cos v\) \(\frac{dv}{1 + \cos v} = dx\) \(\int \frac{dv}{2 \cos^2 \left(\frac{v}{2}\right)} = \int dx\) \(\tan \left(\frac{v}{2}\right) = x + c\) \(\tan \left(\frac{x+y+3}{2}\right) = x + c\)…