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## TN State Board 12th Maths Model Question Paper 3 English Medium

Instructions:

- The question paper comprises of four parts.
- You are to attempt all the parts. An internal choice of questions is provided wherever applicable.
- questions of Part I, II. III and IV are to be attempted separately
- Question numbers 1 to 20 in Part I are objective type questions of one -mark each. These are to be answered by choosing the most suitable answer from the given four alternatives and writing the option code and the corresponding answer
- Question numbers 21 to 30 in Part II are two-marks questions. These are to be answered in about one or two sentences.
- Question numbers 31 to 40 in Parr III are three-marks questions, These are to be answered in about three to five short sentences.
- Question numbers 41 to 47 in Part IV are five-marks questions. These are to be answered) in detail. Draw diagrams wherever necessary.

Time: 3 Hours

Maximum Marks: 90

Part – I

I. Choose the correct answer. Answer all the questions. [20 × 1 = 20]

Question 1.

If A is a 3 × 3 non-singular matrix such that AA^{T} = A^{T} A and B = A^{-1} A^{T}, then BB^{T} = ________.

(a) A

(b) B

(c) I_{3}

(d) B^{T}

Answer:

(c) I_{3}

Question 2.

The rank of the matrix \(\left[\begin{array}{cc}

7 & -1 \\

2 & 1

\end{array}\right]\) is ________.

(a) 9

(b) 2

(c) 1

(d) 5

Answer:

(b) 2

Question 3.

The value of \(\sum_{i=1}^{13}\left(i^{n}+i^{n-1}\right)\) is ________.

(a) 1 + i

(b) i

(c) 1

(d) 0

Answer:

(a) 1 + i

Question 4.

Which of the following is incorrect?

(d) Re(z) ≤ |z|

(b) Im (z) ≤ |z|

(c) \(z \bar{z}=|z|^{2}\)

(d) Re(z) ≥ |z|

Answer:

(d) Re(z) ≥ |z|

Question 5.

According to the rational root theorem, which number is not possible rational zero of 4x^{7} + 2x^{4} – 10x^{3} – 5?

(a) -1

(b) \(\frac{5}{4}\)

(c) \(\frac{4}{5}\)

(d)5

Answer:

(c) \(\frac{4}{5}\)

Question 6.

If \(\cot ^{-1}(\sqrt{\sin \alpha})+\tan ^{-1}(\sqrt{\sin \alpha})=u\), then cos 2u is equal to ______.

(a) tan^{2} α

(b) o

(c) -1

(d) tan 2α

Answer:

(c) -1

Question 7.

The domain of the function defined by f(x) = sin^{-1} \(\sqrt{x-1}\) is _______.

(a) [1, 2]

(b) [-1, 1]

(c) [0, 1]

(d) [-1, 0]

Answer:

(a) [1, 2]

Question 8.

The area of quadrilateral formed with foci of the hyperbolas \(\frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=1\) and \(\frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=-1\) is ________.

(a) 4(a^{2} + b^{2})

(b) 2(a^{2} + b^{2})

(c) a^{2} + b^{2}

(d) \(\frac{1}{2}\) (a^{2} + b^{2})

Answer:

(b) 2(a^{2} + b^{2})

Question 9.

The directrix of the parabola x^{2} = -4y is ________.

(a) x = 1

(b) x = 0

(c) y = 1

(d) y = 0

Answer:

(c) y = 1

Question 10.

If the line \(\frac{x-2}{3}=\frac{y-1}{-5}=\frac{z+2}{2}\) lies in the plane x + 3y – αz + b = β, then (α, β) is ______

(a) (-5, 5)

(b) (-6, 7)

(c) (5, -5)

(d) (6, -7)

Answer:

(b) (-6, 7)

Question 11.

If \(\vec{a} \times(\vec{b} \times \vec{c})=(\vec{a} \times \vec{b}) \times \vec{c}\) for non-coplanar vectors \(\vec{a}, \vec{b}, \vec{c}\) then ________.

(a) \(\vec{a}\) parallel to \(\vec{b}\)

(b) \(\vec{b}\) parallel to \(\vec{c}\)

(c) \(\vec{c}\) parallel to \(\vec{a}\)

(d) \(\vec{a}+\vec{b}+\vec{c}=\overrightarrow{0}\)

Answer:

(c) \(\vec{c}\) parallel to \(\vec{a}\)

Question 12.

The maximum product of two positive numbers, when their sum of the squares is 200, is ________.

(a) 100

(b) \(25 \sqrt{7}\)

(c) 28

(d) \(24 \sqrt{14}\)

Answer:

(a) 100

Question 13.

If w(x,y, z) = x^{2} (y – z) + y^{2} (z – x) + z^{2} (x – y), then \(\frac{\partial w}{\partial x}+\frac{\partial w}{\partial y}+\frac{\partial w}{\partial z}\) is ________.

(a) xy + yz + zx

(b) x (y + z)

(c) y (z + x)

(d) 0

Answer:

(d) 0

Question 14.

If u (x, y) = x^{2} + 3xy + y – 2019, then \(\left.\frac{\partial u}{\partial x}\right|_{(4,-5)}\) is equal to ______.

(a) -4

(b) -3

(c) -7

(d) 13

Answer:

(c) -7

Question 15.

The volume of solid of revolution of the region bounded by y^{2} = x (a – x) about x-axis is ________.

Answer:

(d) \(\frac{\pi a^{3}}{6}\)

Question 16.

\(\int_{0}^{a} f(x) d x+\int_{0}^{a} f(2 a-x) d x\) = _________.

Answer:

(c) \(\int_{0}^{2 a} f(x) d x\)

Question 17.

The differential equation of the family of curves y = Ae^{x} + Be^{-x}, where A and B are arbitrary constants is _______.

Answer:

(b) \(\frac{d^{2} y}{d x^{2}}-y=0\)

Question 18.

The differential equation corresponding to xy = c^{2} where c is an arbitrary constant, is ______.

(a) xy”+ x = 0

(b) y” = 0

(c) xy’ + y = 0

(d) xy”- x = 0

Answer:

(c) xy’ + y = 0

Question 19.

If \(f(x)=\left\{\begin{array}{ll}

2 x, & 0 \leq x \leq a \\

0 & , \text { otherwise }

\end{array}\right.\)

is a probability density function of a random variable, then the value of a is _________.

(a) 1

(b) 2

(c) 3

(d) 4

Answer:

(a) 1

Question 20.

The proposition \(p \wedge(\neg p \vee q)\) is

(a) a tautology

(b) a contradiction

(c) logically equivalent to p ∧ q

(d) logically equivalent to p ∨ q

Answer:

(c) logically equivalent to p ∧ q

Part – II

II. Answer any seven questions. Question No. 30 is compulsory. [7 × 2 = 14]

Question 21.

A 12 metre tall tree was broken into two parts. It was found that the height of the part which was left standing was the cube root of the length of the part that was cut away. Formulate this into a mathematical problem to find the height of the part which was cut away.

Answer:

Let the two parts be x and (12 – x)

Given that x = \(\sqrt[3]{12-x}\)

Cubing on both side, x^{3} = 12 – x

x^{3} + x – 12 = 0

Question 22.

Find the value of \(\sin ^{-1}\left(\sin \frac{5 \pi}{9} \cos \frac{\pi}{9}+\cos \frac{5 \pi}{9} \sin \frac{\pi}{9}\right)\)

Answer:

Question 23.

Obtain the equation of the circles with radius 5 cm and touching x-axis at the origin in general form.

Answer:

Given radius = 5 cm and the circle is touching x axis

So centre will be (0, ± 5) and radius = 5

The equation of the circle with centre (0, ± 5) and radius 5 units is

(x – 0)^{2} + (y ± 5)^{2} = 5^{2}

(i.e) x^{2} + y^{2} ± 10y + 25 – 25 = 0

(i.e) x^{2} + y^{2} ± 10y = 0

Question 24.

Find the length of the perpendicular from the origin to the plane.

\(\bar{r} \cdot(3 \vec{i}+4 \bar{j}+12 \vec{k})=26\).

Answer:

Taking the equation of the plane in cartesian form we get,

\((x \vec{i}+y \vec{j}+z \vec{k}) \cdot(3 \vec{i}+4 \vec{j}+12 \vec{k})=26\)

i.e. 3x + 4y + 12z – 26 = 0

The length of the perpendicular from (0, 0, 0) to the above plane is

Question 25.

Evaluate \(\lim _{x \rightarrow \pi / 2} \frac{\log (\sin x)}{(\pi-2 x)^{2}}\)

Answer:

Note that here l’ Hospitals rule, applied twice yields the result.

Question 26.

Evaluate \(\int_{-1}^{1} e^{-\lambda x}\left(1-x^{2}\right) d x\)

Answer:

Taking u = 1 – x^{2} and v= e^{-λx}, and applying the Bernoulli’s formula, we get

Question 27.

Solve: \(\frac{d y}{d x}+2 y=e^{-x}\)

Answer:

Given that \(\frac{d y}{d x}+2 y=e^{-x}\)

This is a linear differential equation.

Here P = 2; Q = e

∫P dx = ∫2 dx = 2x

Thus, I.F = e^{∫Pdx} = e^{2x}

Hence the solution of (1) is \(y e^{\int \mathrm{P} d x}=\int \mathrm{Q} e^{\int \mathrm{P} d x} d x+c\)

That is, ye^{2x} = ∫e^{-x} e^{2x} dx + c (or) ye^{2x} = e^{x} + c (or) y = e^{-x} + ce^{-2x} is the required solution.

Question 28.

Three fair coins are tossed simultaneously. Find the probability mass function for number of heads occurred.

Answer:

When three coins are tossed, the sample space is

S = {HHH, HHT, HTH, HTT, THH, THT, TTH, TTT}

‘X’ is the random variable denotes the number of heads.

∴ ‘X’ can take the values of 0, 1, 2 and 3

Hence, the probabilities

P(X = 0) = P (No heads) = \(\frac{1}{8}\);

P(X = 1) = P (1 head) = \(\frac{3}{8}\);

P(X = 2) = P (2 heads) = \(\frac{3}{8}\);

P(X = 3) = P (3 heads)= \(\frac{1}{8}\);

∴ The probability mass function is

\(f(x)=\left\{\begin{array}{lll}

1 / 8 & \text { for } & x=0,3 \\

3 / 8 & \text { for } & x=1,2

\end{array}\right.\)

Question 29.

Construct the truth table for \((p \vee q) \vee \neg q\)

Answer:

truth table for \((p \vee q) \vee \neg q\)

Question 30.

Show that f(x, y) = \(\frac{x^{2}-y^{2}}{y^{2}+1}\) is continuous at every (x, y) ∈ R^{2}.

Answer:

Here, f satisfies all the three conditions of continuity at (a, b). Hence, f is continuous at every point of R^{2} as (a, b) ∈ R^{2}.

Part – III

III. Answer any seven questions. Question No. 40 is compulsory. [7 × 3 = 21]

Question 31.

Form a polynomial equation with integer coefficients with \(\sqrt{\frac{\sqrt{2}}{\sqrt{3}}}\) as a root.

Question 32.

Find the equation of the tangents from the point (2, -3) to the parabola y^{2} = 4x

Question 33.

Find the vector and cartesian equations of the straight line passing through the points (-5, 2, 3) and (4,-3, 6).

Question 34.

Find the points on the curve y = x^{3} – 6x^{2} + x + 3 where the normal is parallel to the line x + y =1729.

Question 35.

Assuming log_{10} e = 0.4343, find an approximate value of log_{10} 1003.

Question 36.

Evaluate: \(\int_{0}^{\frac{\pi}{2}} \sin ^{2} x \cos ^{4} x d x\)

Question 37.

Solve the differential equation: \(\frac{d y}{d x}\) = e^{x+y} + x^{3} e^{y}

Question 38.

Using binomial distribution find the mean and variance of X for the following experiments

(i) A fair coin is tossed 100 times, and X denote the number of heads.

(ii) A fair die is tossed 240 times, and X denote the number of times that four appeared.

Question 39.

Let

be any three Boolean matrices of the same type. Find (A ∨ B) ∧C

Question 40.

Sketch the graph of y = sin\(\left(\frac{1}{3} x\right)\) for 0 ≤ x < 6π.

Part – IV

IV. Answer all the questions. [7 × 5 = 35]

Question 41.

(a) A fish tank can be filled in 10 minutes using both pumps A and B simultaneously. However, pump B can pump water in or out at the same rate. If pump B is inadvertently run in reverse, then the tank will be filled in 30 minutes. How long would it take each pump to fill the tank by itself ? (Use Cramer’s rule to solve the problem).

[OR]

(b) Using elementary transformations find the inverse of the matrix \(\left[\begin{array}{ccc}

1 & 3 & -2 \\

-3 & 0 & -5 \\

2 & 5 & 0

\end{array}\right]\)

Question 42.

42. (a) Let z_{1}, z_{2}, and z_{3} be complex numbers such that |z_{1}| = |z_{2}| = |z_{3}| = r > 0 and z_{1} +z_{2} + z_{3} ≠ 0.

Prove that \(\left|\frac{z_{1} z_{2}+z_{2} z_{3}+z_{3} z_{1}}{z_{1}+z_{2}+z_{3}}\right|=r\)

[OR]

(b) Find all cube roots of \(\sqrt{3}\) + i.

Question 43.

(a) Find all zeros of the polynomial x^{6} – 3x^{5} – 5x^{4} + 22x^{3} – 39x^{2} – 39x + 135, if it is known that 1 + 2i and \(\sqrt{3}\) are two of its zeros.

[OR]

(b) Let W(x, y, z) = x^{2} – xy + 3 sin z, x, y, z∈R. Find the linear approximation at (2, -1, 0)

Question 44.

(a) Prove p → (q → r) ≡ (p ∧ q) → r without using truth table.

[OR]

(b) Evaluate \(\int_{0}^{\frac{\pi}{4}} \frac{1}{\sin x+\cos x} d x\)

Question 45.

(a) Prove that \(\text { (i) } \tan ^{-1} \frac{2}{11}+\tan ^{-1} \frac{7}{24}=\tan ^{-1} \frac{1}{2} \text { (ii) } \sin ^{-1} \frac{3}{5}-\cos ^{-1} \frac{12}{13}=\sin ^{-1} \frac{16}{65}\)

[OR]

(b) Find two positive numbers whose product is 100 and whose sum is minimum.

Question 46.

(a) If X is the random variable with distribution function F (x) given by,

\(\mathrm{F}(x)=\left\{\begin{array}{ll}

0, & x<0 \\

\frac{1}{2}\left(x^{2}+x\right) & 0 \leq x<1 \\

1, & x \geq 1

\end{array}\right.\)

then find (i) the probability density function f(x) (ii) P(0.3 ≤ X ≤ 0.6)

[OR]

(b) Find the vertex, focus, equation of directrix and length of the latus rectum of the following: y^{2} – 4y – 8x + 12 = 0

Question 47.

(a) The rate at which the population of a city increases at any time is proportional to the population at that time. If there were 1,30,000 people in the city in 1960 and 1,60,000 in 1990, what population may be anticipated in 2020? [log_{e} \(\left(\frac{16}{3}\right)\) = 0.2070; e^{-0.42} = 1.52]

[OR]

(b) Find the parametric vector, non-parametric vector and Cartesian form of the equation of the plane passing through the point (3, 6, -2), (-1, -2, 6) and (6, 4, -2).