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JEE Advanced 2026 · Inverse Trigonometric Functions

Considering only the principal values of the inverse trigonometric functions, the value of cot⁡−1(cot⁡(−11))+10sin⁡(2cos⁡−1(12))+10sin⁡(2tan⁡−1(2))\cot^{-1}(\cot(-11)) + 10\sin\left(2\cos^{-1}\left(\frac{1}{\sqrt{2}}\right)\right) + 10\sin\left(2\tan^{-1}(2)\right) is

Answer: C. 4π+74\pi+7

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Written solution

E=cot⁡−1(cot⁡(−11))+10sin⁡ ⁣(2cos⁡−112)+10sin⁡ ⁣(2tan⁡−12)E = \cot^{-1}(\cot(-11)) + 10\sin\!\left(2\cos^{-1}\tfrac{1}{\sqrt{2}}\right) + 10\sin\!\left(2\tan^{-1}2\right)

To find E using principal values\text{To find } E \text{ using principal values}

choose the correct option\text{choose the correct option}

1. cot⁡−1(cot⁡(−11)) to its principal value1.\ \cot^{-1}(\cot(-11)) \text{ to its principal value}

2. 10sin⁡ ⁣(2cos⁡−112)2.\ 10\sin\!\left(2\cos^{-1}\tfrac{1}{\sqrt2}\right)

3. 10sin⁡ ⁣(2tan⁡−12)3.\ 10\sin\!\left(2\tan^{-1}2\right)

cot⁡−1:range (0,π)\cot^{-1}: \text{range } (0,\pi)

cot⁡(θ+π)=cot⁡θ⇒cot⁡(−11)=cot⁡(−11+kπ)\cot(\theta+\pi)=\cot\theta \Rightarrow \cot(-11)=\cot(-11+k\pi)

−11+4π≈1.566∈(0,π)✓-11+4\pi \approx 1.566 \in (0,\pi) \quad ✓

cot⁡−1(cot⁡(−11))=4π−11\cot^{-1}(\cot(-11)) = 4\pi - 11

cos⁡−112=π4 ⇒ 2cos⁡−112=π2\cos^{-1}\tfrac{1}{\sqrt2}=\tfrac{\pi}{4}\ \Rightarrow\ 2\cos^{-1}\tfrac{1}{\sqrt2}=\tfrac{\pi}{2}

10sin⁡π2=10⋅1=1010\sin\tfrac{\pi}{2} = 10\cdot 1 = 10

θ=tan⁡−12⇒tan⁡θ=2\theta=\tan^{-1}2 \Rightarrow \tan\theta=2

sin⁡2θ=2tan⁡θ1+tan⁡2θ\sin 2\theta = \frac{2\tan\theta}{1+\tan^2\theta}

sin⁡2θ=2⋅21+22=45\sin 2\theta = \frac{2\cdot 2}{1+2^2} = \frac{4}{5}

10sin⁡(2tan⁡−12)=10⋅45=810\sin(2\tan^{-1}2) = 10\cdot\tfrac{4}{5} = 8

E=(4π−11)+10+8=4π+7E = (4\pi - 11) + 10 + 8 = 4\pi + 7

E=4π+7 ⇒ option (3)\boxed{E = 4\pi+7 \ \Rightarrow\ \text{option (3)}}

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