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JEE Main 2021 · MathsMultiple choiceSingle correctMediumMulti-step

JEE Main 25 February 2021, Shift 1, Maths Q72

Question 72 of 90 in this shift, Maths question 12 of 30, Section A.

If the curves,

\frac{x^2}{a} + \frac{y^2}{b} = 1

and

\frac{x^2}{c} + \frac{y^2}{d} = 1

intersect each other at an angle of

90^\circ

, then which of the following relations is TRUE ?

(1) $a + b = c + d$
(2) $a - b = c - d$ Official answer
(3) $ab = \frac{c+d}{a+b}$
(4) $a - c = b + d$

Official answer

Option 2

NTA final key.

Chapter: Application of Derivatives
Topic: Tangents and Normals
Idea tested: Orthogonal Intersection of Curves

Same idea in other shifts

Asked 2× in all

25 Feb 2021, Shift 2 · Q85If the curves $x = y^4$ and $xy = k$ cut at right angles, then $(4k)^6$ is equal to ________.MediumNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.