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TS EAMCET · Maths · Differential Equations

If \(y=\sin x+A \cos x\) is the general solution of \(\frac{d y}{d x}+f(x) y=\sec x\), then an integrating factor of the differential equation is

  1. A \(\sec x\)
  2. B \(\tan x\)
  3. C \(\cos x\)
  4. D \(\sin x\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\sec x\)

Step-by-step Solution

Detailed explanation

\(y=\sin x+A \cos x\)..(i) \(\frac{d y}{d x}=\cos x-A \sin x\)..(ii) From (i) and (ii), we get \(\cos x \frac{d y}{d x}+y \sin x=1 \Rightarrow \frac{d y}{d x}+\tan x \cdot y=\sec x\) \(\Rightarrow f(x)=\tan x ;\) I.F \(=e^{\int \tan x d x}=\mathrm{e}^{\ln |\sec x| d x}=\sec x\)