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Vidaara.orgClass 12 · Mathematics
CodeVID-M12-05-IMP-01
Implicit, Logarithmic & Parametric Differentiation — Assignment
Chapter: Continuity and Differentiability
Topic: Implicit, Logarithmic & Parametric Differentiation
Maximum Marks: 35
Time: 75 minutes
Name: ____________________ Roll No.: __________ Date: ____________

General Instructions

  • All questions are compulsory.
  • Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
  • Show all working for Sections B, C and D. Only final answers are given at the end — for full solutions, raise your doubts with your teacher.
Section A — Multiple Choice Questions 5 × 1 = 5 marks
1.
For $x^2+y^2=25$, $\dfrac{dy}{dx}=$
  • A.$-\tfrac{x}{y}$
  • B.$\tfrac{x}{y}$
  • C.$-\tfrac{y}{x}$
  • D.$\tfrac{y}{x}$
2.
$\dfrac{d}{dx}x^{x}=$
  • A.$x\cdot x^{x-1}$
  • B.$x^{x}(1+\ln x)$
  • C.$x^{x}\ln x$
  • D.$x^x$
3.
If $x=at^2,\ y=2at$, then $\dfrac{dy}{dx}=$
  • A.$t$
  • B.$\tfrac1t$
  • C.$\tfrac{1}{2t}$
  • D.$2t$
4.
$\dfrac{d^2}{dx^2}(x^3)=$
  • A.$3x^2$
  • B.$6x$
  • C.$6$
  • D.$x^2$
5.
In implicit differentiation, $y$ is treated as:
  • A.a constant
  • B.a function of $x$
  • C.zero
  • D.$x$
Section B — Short Answer (2 marks) 4 × 2 = 8 marks
6.
Find $\dfrac{dy}{dx}$ if $xy=1$.
7.
Differentiate $y=x^{x}$.
8.
If $x=t^2,\ y=t^3$, find $\dfrac{dy}{dx}$.
9.
Find $\dfrac{d^2y}{dx^2}$ if $y=x^4$.
Section C — Short Answer (3 marks) 4 × 3 = 12 marks
10.
Find $\dfrac{dy}{dx}$ if $x^2+xy+y^2=0$.
11.
Differentiate $y=x^{\sin x}$.
12.
If $x=a\cos\theta,\ y=a\sin\theta$, find $\dfrac{dy}{dx}$.
13.
Find $\dfrac{dy}{dx}$ if $y=x^{\ln x}$.
Section D — Long Answer (5 marks) 2 × 5 = 10 marks
14.
If $x=a(\theta-\sin\theta),\ y=a(1-\cos\theta)$, find $\dfrac{dy}{dx}$.
15.
If $x^{y}=e^{x-y}$, prove that $\dfrac{dy}{dx}=\dfrac{\ln x}{(1+\ln x)^2}$.

Answer Key

Section A — Multiple Choice Questions
  1. (A) $-\tfrac{x}{y}$
  2. (B) $x^{x}(1+\ln x)$
  3. (B) $\tfrac1t$
  4. (B) $6x$
  5. (B) a function of $x$
Section B — Short Answer (2 marks)
  1. $-\dfrac{y}{x}$ (i.e. $-\tfrac{1}{x^2}$).
  2. $x^{x}(1+\ln x)$.
  3. $\dfrac{3t}{2}$.
  4. $12x^2$.
Section C — Short Answer (3 marks)
  1. $-\dfrac{2x+y}{x+2y}$.
  2. $x^{\sin x}\!\left(\cos x\ln x+\dfrac{\sin x}{x}\right)$.
  3. $-\cot\theta$.
  4. $x^{\ln x}\cdot\dfrac{2\ln x}{x}$.
Section D — Long Answer (5 marks)
  1. $\cot\dfrac{\theta}{2}$.
  2. $\dfrac{dy}{dx}=\dfrac{\ln x}{(1+\ln x)^2}$.
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