CUET · MATHS · PYQ PAPER 2023

If \(y = x + \tan x\), then value of \(\frac{d^2y}{dx^2}\) at \(x = \frac{\pi}{4}\) is:

A 1
B 2
C 4
D 2\(\sqrt{2}\)

Verified Solution

Answer & Solution

Correct Answer

(C) 4

Step-by-step Solution

Detailed explanation

\( \frac{dy}{dx} = 1 + \sec^2 x \) \( \frac{d^2y}{dx^2} = 2\sec x (\sec x \tan x) = 2\sec^2 x \tan x \) \( \frac{d^2y}{dx^2} \Big|_{x = \frac{\pi}{4}} = 2\left(\sec \frac{\pi}{4}\right)^2 \tan \frac{\pi}{4} = 2(\sqrt{2})^2 (1) = 4 \)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Match the electromagnetic waves in Column-I with production methods in Column-II

Column-I (Electromagnetic Waves)	Column-II (Production Methods)
(A) Microwaves	(I) LC oscillator
(B) Infrared	(II) Magnetron
(C) X-rays	(III) Vibration of atoms/molecules
(D) Radio waves	(IV) Bombarding large atomic number metal target with fast-moving electrons

Choose the correct answer from the options given below :

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