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TS EAMCET · Maths · Trigonometric Ratios & Identities

If \((\sin \theta-\operatorname{cosec} \theta)^2+(\cos \theta+\sec \theta)^2=5\) and \(\theta\) lies in the third quadrant, then \((\sin \theta+\cos \theta)^3=\)

  1. A \(-2 \sqrt{2}\)
  2. B \(2 \sqrt{2}\)
  3. C \(4\)
  4. D \(-4\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(-2 \sqrt{2}\)

Step-by-step Solution

Detailed explanation

\begin{gathered}(\sin \theta-\operatorname{cosec} \theta)^2+(\cos \theta+\sec \theta)^2=5 \\ \sin ^2 \theta+\operatorname{cosec}^2 \theta-2+\cos ^2 \theta+\sec ^2 \theta+2=5 \\ 1+\cot ^2 \theta+1+\tan ^2 \theta=4 \Rightarrow \tan ^2 \theta+\frac{1}{\tan ^2 \theta}=2 \\…