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If sinθ + cosecθ = 2 then the value of sin8θ+cosec8θ\text{sin}^8\text{θ}+\text{cosec}^8\text{θ}sin8θ+cosec8θ​ is:
Question

If sinθ + cosecθ = 2 then the value of sin8θ+cosec8θ\text{sin}^8\text{θ}+\text{cosec}^8\text{θ}​ is:

A.

2

B.

282^8​​

C.

1

D.

242^4​​

Correct option is A

Given:

sinθ+cosecθ=2\sin\theta + \cosec\theta = 2

Concept Used:

cosecθ=1sinθ\cosec\theta = \frac{1}{\sin\theta} ​​

Solution:
Let x = sinθ \sin\theta​, then cosecθ=1x\cosec\theta = \frac{1}{x}​​

So, When ​x+1x=2x + \frac{1}{x} = 2, then x must be equal to 1.

sin8θ+cosec8θ\text{sin}^8\text{θ}+\text{cosec}^8\text{θ}x8+1x8=18+18=1+1=2x^8 + \frac{1}{x^8} = 1^8 + 1^8 = 1 + 1 = 2

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