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Tamil Nadu State Board · CLASS 12th · Maths

TAMIL NADU STATE BOARD CLASS 12 MATHS 2021

76 questions from this CLASS 12th Maths paper. Log in as a CLASS 12th student to view solutions.

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Q1 mcq 1 mark
The inverse of $\begin{bmatrix} 3 & 1 \\ 5 & 2 \end{bmatrix}$ is :
  • A. $\begin{bmatrix} 3 & -1 \\ -5 & 2 \end{bmatrix}$
  • B. $\begin{bmatrix} 2 & -1 \\ -5 & 3 \end{bmatrix}$
  • C. $\begin{bmatrix} -3 & 5 \\ 1 & -2 \end{bmatrix}$
  • D. $\begin{bmatrix} 2 & -5 \\ -1 & 3 \end{bmatrix}$

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Q2 mcq 1 mark
The centre of the hyperbola $\frac{(x-1)^2}{16} - \frac{(y-1)^2}{25} = 1$ is :
  • A. $(\frac{1}{2}, \frac{1}{2})$
  • B. $(-1, 1)$
  • C. $(1, -1)$
  • D. $(0, 0)$

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Q3 mcq 1 mark
The order and degree of the differential equation $\frac{dy}{dx} + \left(\frac{d^2y}{dx^2}\right)^3 = 0$ are :
  • A. 2, 6
  • B. 2, 3
  • C. 2, 4
  • D. 3, 3

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Q4 mcq 1 mark
A pair of dice numbered 1, 2, 3, 4, 5, 6 of a six sided die and 1, 2, 3, 4 of a four sided die is rolled and the sum is determined. If the random variable X denote the sum, then the number of elements in the inverse image of 7 is :
  • A. 3
  • B. 1
  • C. 4
  • D. 2

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Q5 mcq 1 mark
If $|z|=1$, then the value of $\frac{1+z}{1+\frac{1}{z}}$ is :
  • A. $\frac{1}{z}$
  • B. $z$
  • C. 1
  • D. $z$

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Q6 mcq 1 mark
The value of $\int_{-\pi/2}^{\pi/2} \sin^2 x \cos^2 x dx$ is :
  • B. $\frac{3}{2}$
  • C. $\frac{2}{3}$
  • D. $\frac{1}{2}$

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Q7 mcq 1 mark
The function $f(x)=x^2$, in the interval $[0, \infty)$ is :
  • A. cannot be determined
  • B. increasing function
  • C. increasing and decreasing function
  • D. decreasing function

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Q8 mcq 1 mark
The volume of the parallelepiped with its edges represented by the vectors $\vec{i}+\vec{j}, \vec{i}+\vec{j}+\pi\vec{k}$ is :
  • A. $\pi$
  • B. $\frac{2}{\pi}$
  • C. $\frac{4}{\pi}$
  • D. $\frac{3}{\pi}$

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Q9 mcq 1 mark
In the set R of real numbers ‘*’ is defined as follows. Which one of the following is not a binary operation on R ?
  • A. $a * b = a$
  • B. $a * b = \min(a, b)$
  • C. $a * b = a^b$
  • D. $a * b = \max(a, b)$

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Q10 mcq 1 mark
The position of a particle ‘s’ moving at any time t is given by $s(t)=5t^2-2t-8$. The time at which the particle is at rest, is :
  • A. 1
  • C. 3
  • D. 1/3

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Q11 mcq 1 mark
If the function $f(x) = \frac{1}{b-a}$ for $a < x < b$, represents a probability density function of a continuous random variable X, then which of the following cannot be the values of a and b ?
  • A. 7 and 19
  • B. 0 and 12
  • C. 16 and 24
  • D. 5 and 17

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Q12 mcq 1 mark
If $P(x, y)$ be any point on $16x^2 - 125y^2 = 400$ with foci $F_1(3, 0)$ and $F_2(-3, 0)$, then $|PF_1 - PF_2|$ is :
  • A. 10
  • B. 8
  • C. 12
  • D. 6

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Q13 mcq 1 mark
If the planes $\vec{r} \cdot (2\vec{i} - \lambda\vec{j} + \vec{k}) = 0$ and $\vec{r} \cdot (4\vec{i} + 5\vec{j} - \mu\vec{k}) = 0$ are parallel, then the values of $\lambda$ and $\mu$ are respectively :
  • A. $\frac{1}{2}, -2$
  • B. $\frac{1}{2}, -\frac{1}{2}$
  • C. $\frac{1}{2}, 2$
  • D. $\frac{1}{2}, -2$

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Q14 mcq 1 mark
A zero of $x^3 + 64$ is :
  • A. 4i
  • C. -4
  • D. 4

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Q15 mcq 1 mark
The solution of $\frac{dy}{dx} + P(x)y = 0$ is :
  • A. $x = ce^{-\int P dy}$
  • B. $y = ce^{\int P dx}$
  • C. $x = ce^{\int P dy}$
  • D. $y = ce^{-\int P dx}$

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Q16 mcq 1 mark
$\int_{0}^{\pi/2} \sin^7 x dx$ =
  • A. $\pi/2$
  • B. $\int_{0}^{\pi/2} \cos^7 x dx$
  • D. 1

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Q17 mcq 1 mark
The value of $\sin^{-1} \frac{1}{2} + \cos^{-1} \frac{1}{2}$ is :
  • B. $\pi/2$
  • C. $\pi/3$
  • D. $\pi$

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Q18 mcq 1 mark
If A, B and C are invertible matrices of some order, then which one of the following is not true ?
  • A. $\det(A^{-1}) = (\det A)^{-1}$
  • B. $\text{adj } A = |A|A^{-1}$
  • C. $(ABC)^{-1} = C^{-1}B^{-1}A^{-1}$
  • D. $\text{adj }(AB) = (\text{adj } A)(\text{adj } B)$

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Q19 mcq 1 mark
The value of the complex number $(i^{25})^3$ is equal to :
  • A. 1
  • B. i
  • C. -i
  • D. -1

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Q20 mcq 1 mark
If we measure the side of a cube to be 4 cm with an error of 0.1 cm, then the error in calculation of the volume is (in cubic cm) :
  • A. 2
  • B. 0.4
  • C. 4.8
  • D. 0.45

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Q21 long answer
Show that the three vectors $2\hat{i} + 3\hat{j} + 2\hat{k}$, $\hat{i} - \hat{j} + \hat{k}$ and $3\hat{i} + 3\hat{j} + \hat{k}$ are coplanar.

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Q22 long answer
Prove that $\lim_{x \to \infty} \frac{x^m}{e^x}$, where $m$ is a positive integer, is $\infty$.

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Q23 short answer
If $g(x) = x^2 + 1 \sin x$, then find $dg$.

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Q24 long answer
Show that the solution of $\frac{dy}{dx} = \frac{1-y^2}{1-x^2}$ is $\sin^{-1} y = \sin^{-1} x + C$ (or) $\sin^{-1} x = \sin^{-1} y + C$.

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Q25 long answer
If $X$ is the random variable with distribution function $F(x)$, given by: $F(x) = 0$; $x < 0$ $F(x) = x^2$; $0 \le x < 1$ $F(x) = 1$; $1 \le x$ then prove that the p.d.f. is $f(x) = 0$; $x \le 0$ $f(x) = 2x$; $0 < x < 1$ $f(x) = 0$; otherwise

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Q26 long answer
The probability density function of $X$ is given by $f(x) = k e^{-2x}$ for $x > 0$, $0$ for $x \le 0$. Prove that the value of $k$ is $2$.

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Q27 long answer
Show that the differential equation corresponding to $y = A \sin x$, where $A$ is an arbitrary constant, is $\frac{dy}{dx} = y \tan x$.

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Q28 long answer
Show that the rank of the matrix $\begin{bmatrix} 0 & 1 & 2 & 1 \\ 0 & 2 & 4 & 3 \\ 8 & 1 & 0 & 2 \end{bmatrix}$ is 3.

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Q29 long answer
If $A = \begin{bmatrix} 8 & -4 \\ 5 & -3 \end{bmatrix}$, verify that $A(\text{adj } A) = (\text{adj } A)A = |A|I$.

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Q30 long answer
Show that the points $-\frac{1}{2} + i\frac{\sqrt{3}}{2}$ and $-\frac{1}{2} - i\frac{\sqrt{3}}{2}$ are the vertices of an equilateral triangle of side length $\sqrt{3}$.

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Q31 long answer
If the sides of a cubic box are increased by 1, 2, 3 units respectively to form a cuboid, then the volume is increased by 52 cubic units. Show that the volume of the cuboid is 60 cubic units.

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Q32 long answer
Prove that the equation of the parabola with focus (4, 0) and directrix $x = -4$ is $y^2 = 16x$.

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Q33 long answer
A force $\vec{F} = 3\hat{i} + 10\hat{j} - 3\hat{k}$ acts on a particle which is displaced from the point with position vector $4\hat{i} - 3\hat{j} - 2\hat{k}$ to the point with position vector $6\hat{i} + \hat{j} - 3\hat{k}$. Show that the work done by the force is 69 units.

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Q34 long answer
Show that the point on the curve $y = x^2 - 5x + 4$ at which the tangent is parallel to the line $3x + y = 7$ is (1, 0).

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Q35 long answer
An egg of a particular bird is spherical in shape. If the radius to the inside of the shell is 4 mm and radius to the outside of the shell is 4.2 mm, prove that the approximate volume of the shell is $12.8\pi$ mm$^3$.

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Q36 long answer
Define an operation $*$ on $Q$, the set of all rational numbers, as follows: $a * b = \frac{a+b}{2}$. Examine the closure and commutative properties satisfied by $*$ on $Q$.

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Q37 long answer
Show that $\int_0^1 \frac{x^2}{1+x^2} dx = 1 - \frac{\pi}{4}$.

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Q38 long answer
Solve the system of equations $x - y + 2z = 2$, $2x + y + 4z = 7$, $4x - y + z = 4$ by Cramer’s rule.

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Q39 long answer
A camera is accidentally knocked off an edge of a cliff 400 ft. high. The camera falls a distance of $s = -16t^2$ in $t$ seconds. Show that the camera hits the ground when $t=5$ seconds and also prove that the velocity when it hits the ground is $-160$ ft./sec.

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Q40 long answer
If $z = x + iy$ is a complex number such that $\left| \frac{z-4}{z+4i} \right| = 1$, show that the locus of $z$ is the real axis or $y=0$.

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Q41 long answer
Show that $\int_0^1 \frac{\log(1+x)}{1+x^2} dx = \frac{\pi}{8} \log 2$.

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Q42 long answer
Prove that $\cos^{-1} \frac{1}{3} + \cos^{-1} \frac{1}{4} = \cos^{-1} \frac{17}{12}$.

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Q43 long answer
Find the eccentricity, centre, vertices and foci of the ellipse $\frac{x^2}{16} + \frac{y^2}{9} = 1$ and also draw the rough diagram.

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Q44 long answer
Solve $(e^y + 1) \cos x dx + e^y \sin x dy = 0$.

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Q45 long answer
Show that $(p \to q) \equiv \neg p \vee q$.

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Q46 long answer
Using Vector method, prove that $\cos(A-B) = \cos A \cos B + \sin A \sin B$.

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Q47 long answer
Find two positive numbers whose product is 20 and their sum is minimum.

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Q48 long answer
On lighting a rocket cracker it gets projected in a parabolic path and reaches a maximum height of 4 m when it is 6 m away from the point of projection. Finally it reaches the ground 12 m away from the starting point. Show that the angle of projection is $\tan^{-1} \frac{4}{3}$.

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Q49 long answer
A random variable $X$ has the following probability mass function: $X: 1, 2, 3, 4, 5$; $f(x): k, 2k, 3k, 2k, 3k$. Find: (i) the value of $k$. (ii) $P(2 \le X < 5)$. (iii) $P(3 < X)$.

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Q50 long answer
Show that the area of the region bounded by $3x - 2y = 0$, $x = -3$ and $x = 1$ is $\frac{15}{2}$.

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Q51 long answer
Show that the Cartesian equation of the plane passing through the points (1, 2, 3) and (2, 3, 1) and also perpendicular to the plane $3x - 2y + 4z - 5 = 0$ is $2y + z - 7 = 0$.

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Q52 short answer
X has the following probability mass function: X 1 2 3 4 5 f(x) k 2k 3k 2k 3k Find: (i) the value of k. (ii) P(2 ≤ X < 5). (iii) P(3 < X).

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Q53 mcq 1 mark
$\int_{0}^{\frac{\pi}{2}} \sin^7 x \, dx = $
  • A. \frac{\pi}{2}
  • B. $\int_{0}^{\frac{\pi}{2}} \cos^7 x \, dx$
  • D. 1

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Q54 mcq 1 mark
The order and degree of the differential equation $(\frac{d^2y}{dx^2}) + (\frac{dy}{dx})^3 + x^4 = 0$ are :
  • A. 2, 6
  • B. 2, 3
  • C. 2, 4
  • D. 3, 3

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Q55 mcq 1 mark
If $|z|=1$, then the value of $|z+1| + |z-1|$ is :
  • A. 1/z
  • B. z
  • C. 1
  • D. z^2

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Q56 short answer 2 marks
If $z = (2+3i)(1-i)$ then prove that $\frac{1}{26} z = \frac{5}{26} + \frac{1}{26} i$.

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Q57 short answer 2 marks
If $\alpha$ and $\beta$ are the roots of $x^2-5x+6=0$ then prove that $\alpha^2-\beta^2 = \pm 5$.

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Q58 short answer 2 marks
For what value of x does $\sin x = \sin^{-1} x$?

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Q59 short answer 2 marks
Show that the three vectors $2\vec{i}+3\vec{j}+2\vec{k}, \vec{i}-\vec{j}+\vec{k}$ and $3\vec{i}+2\vec{j}+3\vec{k}$ are coplanar.

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Q60 mcq
then the value of $1/z$ is :
  • A. 1/z
  • B. z
  • C. 1
  • D. z

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Q61 long answer
If $z=(2+3i)(1-i)$ then prove that $z^{-1} = \frac{1}{26} + i \frac{5}{26}$.

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Q62 long answer
Show that the three vectors $2i - 3j + 2k$, $i - j + k$ and $3i + j + k$ are coplanar.

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Q63 long answer
If $X$ is the random variable with distribution function $F(x)$, given by: $F(x) = 0$ for $x < 0$; $F(x) = \frac{1}{2}(x^2+x)$ for $0 \le x < 1$; $F(x) = 1$ for $x \ge 1$, then prove that the p.d.f. is $f(x) = x + \frac{1}{2}$ for $0 < x < 1$; $0$ otherwise.

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Q64 long answer
Show that $\int_0^1 \frac{1}{1+x} dx = \log 2$.

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Q65 mcq 1 mark
The value of $\sin^{-1} \left(\frac{1}{2}\right) + \cos^{-1} \left(\frac{1}{2}\right)$ is :
  • A. $0$
  • B. $\frac{\pi}{2}$
  • C. $\frac{\pi}{3}$
  • D. $\pi$

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Q66 mcq 1 mark
The volume of the parallelepiped with its edges represented by the vectors $\vec{i} + \vec{j} + \vec{k}$, $\vec{i} + 2\vec{j} + \vec{k}$ and $\vec{i} + \vec{j} + \pi\vec{k}$ is :
  • A. $\pi$
  • B. $\frac{\pi}{2}$
  • C. $\frac{\pi}{4}$
  • D. $\frac{\pi}{3}$

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Q67 mcq 1 mark
$\int_0^{\pi/2} \sin^7 x \, dx = \dots$
  • A. $\frac{\pi}{2}$
  • B. $\int_0^{\pi/2} \cos^7 x \, dx$
  • C. $0$
  • D. $1$

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Q68 short answer 2 marks
If $z = (2 + i\sqrt{3}) / (1 - i)$ then prove that $|z| = \sqrt{7/2}$.

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Q69 short answer 2 marks
Show that the solution of $\frac{dy}{dx} = \frac{\sqrt{1-y^2}}{\sqrt{1-x^2}}$ is $\sin^{-1} y = \sin^{-1} x + C$.

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Q70 mcq
If X is a random variable, then which of the following cannot be the values of a and b?
  • A. 7 and 19
  • B. 0 and 12
  • C. 16 and 24
  • D. 5 and 17

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Q71 long answer
Show that $\int_{0}^{1} \frac{dx}{x^2 + x + 1} = \dots$ (incomplete text in source).

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Q72 long answer
Show that $\int_{0}^{1} \dots$ (incomplete text in source).

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Q73 long answer
Prove that $\cos^{-1}(1/3) + \cos^{-1}(4/5) = \cos^{-1}(17/15)$ (check source for correction).

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Q74 long answer
Prove that $\cos^{-1} \left( \frac{1}{3} \right) - \cos^{-1} \left( \frac{1}{4} \right) = \cos^{-1} \left( \frac{1}{12} \right)$.

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Reading Passage

A random variable X has the following probability mass function : X 1 2 3 4 5 f(x) k 2k 3k 2k 3k

Q75 long answer
Find the value of $k$ for the probability mass function where $X: 1, 2, 3, 4, 5$ and $f(x): k, 2k, 3k, 2k, 3k$.

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Q76 long answer
Find $P(2 \le X < 5)$ given the probability mass function.

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