Question:

Evaluate \[ \int \frac{2\cos x+1}{(2+\cos x)^2}\,dx-\frac{\sin x}{2+\cos x} \]

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Before integrating, check whether the integrand is directly the derivative of a given expression. This can simplify the problem immediately.
Updated On: Jun 26, 2026
  • \(\frac{1}{2+\cos x}+C\)
  • \(\sin x+C\)
  • \(\frac{2}{2+\cos x}+C\)
  • \(C\)
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The Correct Option is D

Solution and Explanation

Step 1: Observe the derivative of the second term.
Consider \[ \frac{\sin x}{2+\cos x} \] Differentiate it: \[ \frac{d}{dx}\left(\frac{\sin x}{2+\cos x}\right) = \frac{(2+\cos x)\cos x-\sin x(-\sin x)}{(2+\cos x)^2} \] \[ = \frac{2\cos x+\cos^2x+\sin^2x}{(2+\cos x)^2} \] Using \[ \sin^2x+\cos^2x=1, \] we get \[ \frac{d}{dx}\left(\frac{\sin x}{2+\cos x}\right) = \frac{2\cos x+1}{(2+\cos x)^2} \]

Step 2: Integrate the given integrand.
Thus, \[ \int \frac{2\cos x+1}{(2+\cos x)^2}\,dx = \frac{\sin x}{2+\cos x}+C \]

Step 3: Substitute in the given expression.
Now, \[ \int \frac{2\cos x+1}{(2+\cos x)^2}\,dx-\frac{\sin x}{2+\cos x} \] \[ = \frac{\sin x}{2+\cos x}+C-\frac{\sin x}{2+\cos x} \] \[ =C \]

Step 4: Final conclusion.
Hence, \[ \boxed{C} \]
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