SSC CPO 2023 PYQ — Question 122

SSC CPO - 05 Oct 2023 - Shift 3 • Quantitative Aptitude • Q122

If sinθ\theta + cosθ\theta = 2\sqrt{2} cosθ\theta, then find sinθ−cosθsinθ\frac{sin\theta-cos\theta}{sin\theta}:

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Correct answer: A

Explanation

The correct answer is Option 1 i.e.  -2\sqrt{2}.

sinθ\theta + cosθ\theta = 2\sqrt{2} cosθ\theta 

⇒ (sinθ\theta + cosθ\theta)/cosθ\theta = 2\sqrt{2} 

⇒ tanθ\theta + 1 = 2\sqrt{2}

⇒ tanθ\theta = 2\sqrt{2} - 1

⇒ cotθ\theta = 12−11 \over {\sqrt{2} -1}    ....(1)

Rationalising the above equation (1),

cotθ\theta = 12−1×2+12+1{1 \over \sqrt{2} -1} \times {\frac{\sqrt{2} + 1}{\sqrt{2} + 1}}

⇒ cotθ\theta = 2+1\sqrt{2} + 1

Now, sinθ−cosθsinθ\frac{sin\theta-cos\theta}{sin\theta}

⇒ sinθsinθ−cosθsinθ\frac{sin\theta}{sin\theta} - \frac{cos\theta}{ sin\theta}

⇒ 1−cosθsinθ1 - \frac{cos\theta}{ sin\theta}

⇒ 1−cotθ1 -cot\theta

⇒ 1 - (2+1\sqrt{2} + 1)

⇒ 1 - 2\sqrt {2} - 1

⇒  -2\sqrt{2} 

Hence the required answer is  -2\sqrt{2} .