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JEE Main 20254 AprilMorning Shift
Exam
JEE Main
Year
2025
Date
4 April
Shift
Morning Shift
Subject
Mathematics
Chapter
Trigonometric Equations

JEE Main 2025 · 4 April · Morning Shift · Mathematics · Trigonometric Equations

If 10 ^4 θ+15 ^4 θ=6 , then the value of 27 cosec^6 θ+8 ^6 θ 16 ^8...

If 10sin⁡4θ+15cos⁡4θ=610 \sin ^4 \theta+15 \cos ^4 \theta=6, then the value of 27cosec⁡6θ+8sec⁡6θ16sec⁡8θ\frac{27 \operatorname{cosec}^6 \theta+8 \sec ^6 \theta}{16 \sec ^8 \theta} is:

Options

  1. A25\frac{2}{5}
  2. B34\frac{3}{4}
  3. C35\frac{3}{5}
  4. D15\frac{1}{5}

Correct answer

A. 25\frac{2}{5}

Step-by-step solution

10(sin⁡2θ)2+15(1−sin⁡2θ)2=6 Let sin⁡2θ=t⇒10t2+15(1−t)2=1610t2+15−30t+15t2=625t2−30t+9=0(5t−3)2=0sin⁡2θ=35 and  cos⁡2θ=2527×12527+8+125816(52)4=250125×5=25\begin{aligned} & 10\left(\sin ^2 \theta\right)^2+15\left(1-\sin ^2 \theta\right)^2=6 \\ & \text{ Let } \sin ^2 \theta=\mathrm{t} \Rightarrow 10 \mathrm{t}^2+15(1-\mathrm{t})^2=16 \\ & 10 \mathrm{t}^2+15-30 \mathrm{t}+15 \mathrm{t}^2=6 \\ & 25 \mathrm{t}^2-30 \mathrm{t}+9=0 \\ & (5 \mathrm{t}-3)^2=0 \\ & \sin ^2 \theta=\frac{3}{5} \text{\text{ and } } \cos ^2 \theta=\frac{2}{5} \\ & \frac{27 \times \frac{125}{27}+8+\frac{125}{8}}{16\left(\frac{5}{2}\right)^4}=\frac{250}{125 \times 5}=\frac{2}{5}\end{aligned}
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