Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NDA 2026
Exam
NDA
Year
2026
Subject
Mathematics
Chapter
Continuity and Differentiability

NDA 2026 · Mathematics · Continuity and Differentiability

Passage: Let f(x)= (x^2) and g(x)=x|x| for |x| Question: If q(x)=f...

Passage: Let f(x)=tan⁡(x2)f(x)=\tan(x^2) and g(x)=x∣x∣g(x)=x|x| for ∣x∣<π2|x|< \sqrt{\dfrac{\pi}{2}}.

Question: If q(x)=f∘g(x)q(x)=f{}^{\circ} g(x), then which of the following statements is/are correct ?
I. q(x)q(x) is continuous at x=0x=0.
II. q(x)q(x) is differentiable at x=0x=0.
Select the answer using the code given below :

Options

  1. AI only
  2. BII only
  3. CBoth I and II
  4. DNeither I nor II

Correct answer

C. Both I and II

Step-by-step solution

Given f(x)=tan⁡(x2)f(x) = \tan(x^2) and g(x)=x∣x∣g(x) = x|x|.

The composite function q(x)q(x) is given by:

q(x)=f(g(x))=f(x∣x∣)=tan⁡((x∣x∣)2)q(x) = f(g(x)) = f(x|x|) = \tan((x|x|)^2)

Since (x∣x∣)2=x2∣x∣2=x4(x|x|)^2 = x^2|x|^2 = x^4, we have:

q(x)=tan⁡(x4)q(x) = \tan(x^4)

Checking continuity at x=0x=0:

lim⁡x→0q(x)=lim⁡x→0tan⁡(x4)=0\lim_{x \to 0} q(x) = \lim_{x \to 0} \tan(x^4) = 0

Also, q(0)=tan⁡(0)=0q(0) = \tan(0) = 0. Since lim⁡x→0q(x)=q(0)\lim_{x \to 0} q(x) = q(0), q(x)q(x) is continuous at x=0x=0. Statement I is correct.

Checking differentiability at x=0x=0:

q′(0)=lim⁡x→0q(x)−q(0)x−0=lim⁡x→0tan⁡(x4)xq'(0) = \lim_{x \to 0} \dfrac{q(x) - q(0)}{x - 0} = \lim_{x \to 0} \dfrac{\tan(x^4)}{x}

q′(0)=lim⁡x→0(tan⁡(x4)x4×x3)=1×0=0q'(0) = \lim_{x \to 0} \left( \dfrac{\tan(x^4)}{x^4} \times x^3 \right) = 1 \times 0 = 0

Since the limit exists and is finite, q(x)q(x) is differentiable at x=0x=0. Statement II is correct.

Both statements I and II are correct.

Answer: Both I and II
Practice Continuity and Differentiability on Quantrex Academy →

More from Continuity and Differentiability

What is the derivative of (x)/(|x|) with respect to x , where x< 0 ? NDA 2026Passage: Let f(x)= cases ax(x-1), & x 3 cases Given that f(x) is continuous for all x but… NDA 2026Passage: Let f(x)= (x^2) and g(x)=x|x| for |x| Question: If p(x)=f(x)g(x) , then which of… NDA 2026If f(x) is differentiable at x=a , then consider the following statements : I. f(x) is… NDA 2026Passage: Let f(x)= cases ax(x-1), & x 3 cases Given that f(x) is continuous for all x but… NDA 2026Consider the following for the two (02) items that follow: Let f(x) = cases x^3, & x^2… NDA 2025For the following two (02) items: Let the function f(x) = |x - 3| + |x - 4| be defined on… NDA 2025For the following two (02) items: Consider the function f(x) = cases 4(5^x), & x If the… NDA 2025For the following two (02) items: Let the function f(x) = |x - 3| + |x - 4| be defined on… NDA 2025Consider the following for the two (02) items that follow: Let f(x) = cases x^3, & x^2… NDA 2025Paragraph: Let f(x)=[x]^2- [x^2] . Question: Consider the following statements: A. f(x)… NDA 2024Let f(x)=|x|+1 and g(x)=[x]-1 , where [.] is the greatest integer function. Let… NDA 2024Let f(x)=\ array cl (x-3)/(|x-3|)+a ; & x 3 array .f(x) be continuous at x=3 . What is… NDA 2023Let f(x)=\ array cl (x-3)/(|x-3|)+a ; & x 3 array .f(x) be continuous at x=3 . What is… NDA 2023Let f(x)=\ array cc a x(x+1)+b, & x < 1 x-1 & 1 ≤ x ≤ 2 array . If the function f(x) is… NDA 2023Let f(x)=\ array cc x+6, & x ≤ 1 p x+q, & 1 Question: What is the value of q ? NDA 2023 Full Continuity and Differentiability list Continuity and Differentiability JEE Maths PYQsJEE Mathematics PYQs All NDA PYQs