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JEE Mains · Maths · STD 11 - Trigonometrical equations

यदि समीकरण \(\cos ^{4} \theta+\sin ^{4} \theta+\lambda=0\) के \(\theta\) में वास्तविक हल है, तो \(\lambda\) निम्न में से किस अन्तराल में स्थित है ?

  1. A \(\left[-\frac{3}{2},-\frac{5}{4}\right]\)
  2. B \(\left(-\frac{1}{2},-\frac{1}{4}\right]\)
  3. C \(\left(-\frac{5}{4},-1\right)\)
  4. D \(\left[-1,-\frac{1}{2}\right]\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\left[-1,-\frac{1}{2}\right]\)

Step-by-step Solution

Detailed explanation

\(\lambda=-\left(\sin ^{4} \theta+\cos ^{4} \theta\right)\) \(\lambda=-\left(\sin ^{2} \theta+\cos ^{2} \theta\right)^{2}-2 \sin ^{2} \theta \cos ^{2} \theta\) \(\lambda=\frac{\sin ^{2} 2 \theta}{2}-1\) \(\lambda \in\left[-1,-\frac{1}{2}\right]\)…
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