Mathematics · Hyperbola

JEE Main 2026 — 28 January, Morning Shift — Question 21

For some θ∈(0,π2)\theta \in\left(0, \frac{\pi}{2}\right), let the eccentricity and the length of the latus rectum of the hyperbola x2−y2sec⁡2θ=8x^{2}- \mathrm{y}^{2} \sec ^{2} \theta=8 be e1\mathrm{e}_{1} and ℓ1\ell_{1}, respectively, and let the eccentricity and the length of the latus rectum of the ellipse x2sec⁡2θ+y2=6x^{2} \sec ^{2} \theta+y^{2}=6 be e2e_{2} and ℓ2\ell_{2}, respectively. If e12=e22(sec⁡2θ+1),e_{1}^{2}=e_{2}^{2}\left(\sec ^{2} \theta+1\right), \quad then (ℓ1ℓ2e1e2)tan⁡2θ\left(\frac{\ell_{1} \ell_{2}}{\mathrm{e}_{1} \mathrm{e}_{2}}\right) \tan ^{2} \theta is equal to ____\_\_\_\_ .

Answer: 8

Numerical answer — enter this value.

Step-by-step solution

x28−y28cos⁡2θ=1\frac{x^{2}}{8}-\frac{y^{2}}{8 \cos ^{2} \theta}=1

e1=1+8cos⁡2θ8 e_{1}=\sqrt{1+\frac{8 \cos ^{2} \theta}{8}}

ℓ1=2 b2a=2⋅(8cos⁡2θ)22\ell_{1}=\frac{2 \mathrm{~b}^{2}}{\mathrm{a}}=\frac{2 \cdot\left(8 \cos ^{2} \theta\right)}{2 \sqrt{2}}

x66+y26cos⁡2θ=1\frac{x^{6}}{6}+\frac{y^{2}}{6 \cos ^{2} \theta}=1

e2=1−6cos⁡2θ6=sin⁡θe_{2}=\sqrt{1-\frac{6 \cos ^{2} \theta}{6}}=\sin \theta

ℓ2=2 b2a=2.6cos⁡2θ6\ell_{2}=\frac{2 \mathrm{~b}^{2}}{\mathrm{a}}=\frac{2.6 \cos ^{2} \theta}{\sqrt{6}}

e12=e22(1+sec⁡2θ)\mathrm{e}_{1}^{2}=\mathrm{e}_{2}^{2}\left(1+\sec ^{2} \theta\right)

1+cos⁡2θ=sin⁡2θ(1+1cos⁡2θ)1+\cos ^{2} \theta=\sin ^{2} \theta\left(1+\frac{1}{\cos ^{2} \theta}\right)

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

Solving we get θ=π4\theta=\frac{\pi}{4}

ℓ1=22\ell_{1}=2 \sqrt{2}

e1=32\mathrm{e}_{1}=\sqrt{\frac{3}{2}}

ℓ2=6\ell_{2}=\sqrt{6}

e2=12\mathrm{e}_{2}=\frac{1}{\sqrt{2}}

(ℓ1ℓ2e1e2)tan⁡2θ=8\left(\frac{\ell_{1} \ell_{2}}{\mathrm{e}_{1} \mathrm{e}_{2}}\right) \tan ^{2} \theta=8 \quad (By putting values)

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Subject
Mathematics
Chapter
Hyperbola
Topic
Rectangular Hyperbola