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Question: Answered & Verified by Expert
If \(y=\frac{2 \sin \alpha}{1+\cos \alpha+\sin \alpha}\), then value of \(\frac{1-\cos \alpha+\sin \alpha}{1+\sin \alpha}\) is
MathematicsTrigonometric EquationsBITSATBITSAT 2009
Options:
  • A \(\frac{y}{3}\)
  • B \(\mathrm{y}\)
  • C \(2 y\)
  • D \(\frac{3}{2} y\)
Solution:
1534 Upvotes Verified Answer
The correct answer is: \(\mathrm{y}\)
\(\begin{aligned}
& \frac{1-\cos \alpha+\sin \alpha}{1+\sin \alpha} \\
& =\frac{1-\cos \alpha+\sin \alpha}{1+\sin \alpha} \cdot \frac{1+\cos \alpha+\sin \alpha}{1+\cos \alpha+\sin \alpha} \\
& =\frac{(1+\sin \alpha)^2-\cos ^2 \alpha}{(1+\sin \alpha)(1+\cos \alpha+\sin \alpha)} \\
& =\frac{2 \sin \alpha(1+\sin \alpha)}{(1+\sin \alpha)(1+\cos \alpha+\sin \alpha)} \\
& =\frac{2 \sin \alpha}{1+\cos \alpha+\sin \alpha}=y
\end{aligned}\)

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