SSC CGL 2024 PYQ — Question 70

SSC CGL - 12 Sep 2024 - Shift 3 • Quantitative Aptitude • Q70

If tan 4θ\theta. tan6θ\theta = 1, where tan6θ\theta is an acute angle, then find the value of Cot5θ\theta.

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Correct answer: D

Explanation

The correct answer is option 4 i.e. 1.

⇒ tan⁡(4θ)⋅tan⁡(6θ)=1\tan(4\theta) \cdot \tan(6\theta) = 1

⇒ tan⁡(4θ)⋅tan⁡(6θ)=1\tan(4\theta) \cdot \tan(6\theta) = 1

tan⁡(A)⋅tan⁡(B)=1\tan(A) \cdot \tan(B) = 1

A + B = 90°

⇒ 4θ+6θ=90∘4\theta + 6\theta = 90^\circ

⇒ 10θ=90∘10\theta = 90^\circ

⇒ θ=90∘10=9∘\theta = \frac{90^\circ}{10} = 9^\circ

θ=9∘\theta = 9^\circ   , we can compute (5θ)( 5\theta):

⇒ 5θ=5×9∘=45∘5\theta = 5 \times 9^\circ = 45^\circ

The cotangent of ( 45° ) is:

⇒ cot(45° ) = 1

The value of (cot⁡(5θ))( \cot(5\theta) ) is: 1 .