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TS EAMCET · Maths · Differential Equations

If \(\cos x \frac{d y}{d x}=y \sin x-1, x \neq(2 n+1) \frac{\pi}{2}, n \in \mathrm{Z}\) is the differential equation corresponding to the curve \(y=f(x)\) and \(f(0)=1\) then \(f(x)=\)

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

Answer & Solution

Correct Answer

(A) \((1-x) \sec x\)

Step-by-step Solution

Detailed explanation

\(\frac{d y}{d x} - (\tan x) y = - \sec x\) IF \( = e^{\int -\tan x dx} = e^{\ln |\cos x|} = \cos x\) \(y \cos x = \int (-\sec x \cdot \cos x) dx\) \(y \cos x = \int -1 dx\) \(y \cos x = -x + C\) \(f(0)=1 \Rightarrow 1 \cdot \cos(0) = -0 + C \Rightarrow C=1\)…