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If tanθ + cotθ = 4, then sec2θ × cosec2 θ is equal to:
Question

If tanθ + cotθ = 4, then sec2θ × cosec2 θ is equal to:

A.

12

B.

16

C.

8

D.

24

Correct option is B

Given:
tanθ+cotθ=4\tan\theta + \cot\theta = 4​​
Formula Used:
secθ×cosecθ=tanθ+cotθ\sec\theta × \cosec\theta = \tan\theta + \cot\theta​​
Solution:
Express the given equation in terms of sine and cosine:
sinθcosθ+cosθsinθ=4\frac{\sin\theta}{\cos\theta} + \frac{\cos\theta}{\sin\theta} = 4​​

sin2θ+cos2θsinθcosθ=4\frac{\sin^2\theta + \cos^2\theta}{\sin\theta\cos\theta} = 4​​

Using the identity sin2θ+cos2θ=1: \sin^2\theta + \cos^2\theta = 1:​​

1sinθcosθ=4\frac{1}{\sin\theta\cos\theta} = 4​​

This simplifies to:

secθ×cosecθ=4\sec\theta × \cosec\theta = 4​​

Square both sides of the equation:

sec2θ×cosec2θ=16\sec^2\theta × \cosec^2\theta = 16​​
Final Answer
So the correct answer is (b)

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