Class XII Chapter 8 – Application of Integrals Maths

The area of the region bounded by the lines is the area of ∆ABC. AL and CM are the

perpendiculars on x-axis.

Area (∆ABC) = Area (ALMCA) – Area (ALB) – Area (CMB)

Question 15: , is represented as

Find the area of the region

Answer

The area bounded by the curves,

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Class XII Chapter 8 – Application of Integrals Maths

The points of intersection of both the curves are .

The required area is given by OABCO.

It can be observed that area OABCO is symmetrical about x-axis.

∴ Area OABCO = 2 × Area OBC

Area OBCO = Area OMC + Area MBC

Question 16:

Area bounded by the curve y = x3, the x-axis and the ordinates x = –2 and x = 1 is

A. – 9

B.

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Class XII Chapter 8 – Application of Integrals Maths

C.

D.

Answer

Solve it yourself.

The correct option is D.

Question 17:

The area bounded by the curve , x-axis and the ordinates x = –1 and x = 1 is

given by

[Hint: y = x2 if x > 0 and y = –x2 if x < 0]

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Class XII Chapter 8 – Application of Integrals Maths

A. 0

B.

C.

D.

Answer

Thus, the correct answer is C.

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Class XII Chapter 8 – Application of Integrals Maths

Question 18:

The area of the circle x2 + y2 = 16 exterior to the parabola y2 = 6x is

A.

B.

C.

D.

Answer

The given equations are

x2 + y2 = 16 … (1)

y2 = 6x … (2)

Area bounded by the circle and parabola

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Class XII Chapter 8 – Application of Integrals Maths

Area of circle = π (r)2

= π (4)2

= 16π units

Thus, the correct answer is C.

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Class XII Chapter 8 – Application of Integrals Maths

Question 19:

The area bounded by the y-axis, y = cos x and y = sin x when

A.

B.

C.

D.

Answer

The given equations are

y = cos x … (1)

And, y = sin x … (2)

Required area = Area (ABLA) + area (OBLO)

Integrating by parts, we obtain

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Class XII Chapter 8 – Application of Integrals Maths

Thus, the correct answer is B.

Therefore, the required area is units

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Class XII Chapter 9 – Differential Equations Maths

Question 1: www.ncrtsolutions.blogspot.com

Exercise 9.1

Determine order and degree(if defined) of differential equation

Answer

The highest order derivative present in the differential equation is . Therefore, its

order is four.

The given differential equation is not a polynomial equation in its derivatives. Hence, its

degree is not defined.

Question 2:

Determine order and degree(if defined) of differential equation

Answer

The given differential equation is:

The highest order derivative present in the differential equation is . Therefore, its order

is one.

It is a polynomial equation in . The highest power raised to is 1. Hence, its degree is

one.

Question 3:

Determine order and degree(if defined) of differential equation

Answer

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Class XII Chapter 9 – Differential Equations Maths

The highest order derivative present in the given differential equation is . Therefore,

its order is two.

It is a polynomial equation in and . The power raised to is 1.

Hence, its degree is one.

Question 4:

Determine order and degree(if defined) of differential equation

Answer

The highest order derivative present in the given differential equation is . Therefore,

its order is 2.

The given differential equation is not a polynomial equation in its derivatives. Hence, its

degree is not defined.

Question 5:

Determine order and degree(if defined) of differential equation

Answer

The highest order derivative present in the differential equation is . Therefore, its

order is two.

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Class XII Chapter 9 – Differential Equations Maths

It is a polynomial equation in and the power raised to is 1.

Hence, its degree is one.

Question 6:

Determine order and degree(if defined) of differential equation

Answer

The highest order derivative present in the differential equation is . Therefore, its

order is three.

The given differential equation is a polynomial equation in .

The highest power raised to is 2. Hence, its degree is 2.

Question 7:

Determine order and degree(if defined) of differential equation

Answer

The highest order derivative present in the differential equation is . Therefore, its

order is three.

It is a polynomial equation in . The highest power raised to is 1. Hence, its

degree is 1.

Question 8:

Determine order and degree(if defined) of differential equation

Answer

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Class XII Chapter 9 – Differential Equations Maths

The highest order derivative present in the differential equation is . Therefore, its order

is one.

The given differential equation is a polynomial equation in and the highest power

raised to is one. Hence, its degree is one.

Question 9:

Determine order and degree(if defined) of differential equation

Answer

The highest order derivative present in the differential equation is . Therefore, its

order is two.

The given differential equation is a polynomial equation in and and the highest

power raised to is one.

Hence, its degree is one.

Question 10:

Determine order and degree(if defined) of differential equation

Answer

The highest order derivative present in the differential equation is . Therefore, its

order is two.

This is a polynomial equation in and and the highest power raised to is one.

Hence, its degree is one.

Question 11:

The degree of the differential equation

is

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Class XII Chapter 9 – Differential Equations Maths

(A) 3 (B) 2 (C) 1 (D) not defined

Answer

The given differential equation is not a polynomial equation in its derivatives. Therefore,

its degree is not defined.

Hence, the correct answer is D.

Question 12:

The order of the differential equation

is

(A) 2 (B) 1 (C) 0 (D) not defined

Answer

The highest order derivative present in the given differential equation is . Therefore,

its order is two.

Hence, the correct answer is A.

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Class XII Chapter 9 – Differential Equations Maths

Question 1: Exercise 9.2

Answer

Differentiating both sides of this equation with respect to x, we get:

Now, differentiating equation (1) with respect to x, we get:

Substituting the values of in the given differential equation, we get the L.H.S.

as:

Thus, the given function is the solution of the corresponding differential equation.

Question 2:

Answer

Differentiating both sides of this equation with respect to x, we get:

Substituting the value of in the given differential equation, we get:

L.H.S. = = R.H.S.

Hence, the given function is the solution of the corresponding differential equation.

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Class XII Chapter 9 – Differential Equations Maths

Question 3:

Answer

Differentiating both sides of this equation with respect to x, we get:

Substituting the value of in the given differential equation, we get:

L.H.S. = = R.H.S.

Hence, the given function is the solution of the corresponding differential equation.

Question 4:

Answer

Differentiating both sides of the equation with respect to x, we get:

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Class XII Chapter 9 – Differential Equations Maths

L.H.S. = R.H.S.

Hence, the given function is the solution of the corresponding differential equation.

Question 5:

Answer

Differentiating both sides with respect to x, we get:

Substituting the value of in the given differential equation, we get:

Hence, the given function is the solution of the corresponding differential equation.

Question 6:

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Class XII Chapter 9 – Differential Equations Maths

Answer

Differentiating both sides of this equation with respect to x, we get:

Substituting the value of in the given differential equation, we get:

Hence, the given function is the solution of the corresponding differential equation.

Question 7:

Answer

Differentiating both sides of this equation with respect to x, we get:

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Class XII Chapter 9 – Differential Equations Maths

L.H.S. = R.H.S.

Hence, the given function is the solution of the corresponding differential equation.

Question 8:

Answer

Differentiating both sides of the equation with respect to x, we get:

Substituting the value of in equation (1), we get:

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Class XII Chapter 9 – Differential Equations Maths

Hence, the given function is the solution of the corresponding differential equation.

Question 9:

Answer

Differentiating both sides of this equation with respect to x, we get:

Substituting the value of in the given differential equation, we get:

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Class XII Chapter 9 – Differential Equations Maths

Hence, the given function is the solution of the corresponding differential equation.

Question 10:

Answer

Differentiating both sides of this equation with respect to x, we get:

Substituting the value of in the given differential equation, we get:

Hence, the given function is the solution of the corresponding differential equation.

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Class XII Chapter 9 – Differential Equations Maths

Question 11:

The numbers of arbitrary constants in the general solution of a differential equation of

fourth order are:

(A) 0 (B) 2 (C) 3 (D) 4

Answer

We know that the number of constants in the general solution of a differential equation

of order n is equal to its order.

Therefore, the number of constants in the general equation of fourth order differential

equation is four.

Hence, the correct answer is D.

Question 12:

The numbers of arbitrary constants in the particular solution of a differential equation of

third order are:

(A) 3 (B) 2 (C) 1 (D) 0

Answer

In a particular solution of a differential equation, there are no arbitrary constants.

Hence, the correct answer is D.

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Class XII Chapter 9 – Differential Equations Maths

Question 1: Exercise 9.3

Answer

Differentiating both sides of the given equation with respect to x, we get:

Again, differentiating both sides with respect to x, we get:

Hence, the required differential equation of the given curve is

Question 2:

Answer

Differentiating both sides with respect to x, we get:

Again, differentiating both sides with respect to x, we get:

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Class XII Chapter 9 – Differential Equations Maths

Dividing equation (2) by equation (1), we get:

This is the required differential equation of the given curve.

Question 3:

Answer

Differentiating both sides with respect to x, we get:

Again, differentiating both sides with respect to x, we get:

Multiplying equation (1) with (2) and then adding it to equation (2), we get:

Now, multiplying equation (1) with equation (3) and subtracting equation (2) from it, we

get:

Substituting the values of in equation (3), we get:

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Class XII Chapter 9 – Differential Equations Maths

This is the required differential equation of the given curve.

Question 4:

Answer

Differentiating both sides with respect to x, we get:

Multiplying equation (1) with equation (2) and then subtracting it from equation (2), we

get:

Differentiating both sides with respect to x, we get:

Dividing equation (4) by equation (3), we get:

This is the required differential equation of the given curve.

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Class XII Chapter 9 – Differential Equations Maths

Question 5:

Answer

Differentiating both sides with respect to x, we get:

Again, differentiating with respect to x, we get:

Adding equations (1) and (3), we get:

This is the required differential equation of the given curve.

Question 6:

Form the differential equation of the family of circles touching the y-axis at the origin.

Answer

The centre of the circle touching the y-axis at origin lies on the x-axis.

Let (a, 0) be the centre of the circle.

Since it touches the y-axis at origin, its radius is a.

Now, the equation of the circle with centre (a, 0) and radius (a) is

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Class XII Chapter 9 – Differential Equations Maths

Differentiating equation (1) with respect to x, we get:

Now, on substituting the value of a in equation (1), we get:

This is the required differential equation.

Question 7:

Form the differential equation of the family of parabolas having vertex at origin and axis

along positive y-axis.

Answer

The equation of the parabola having the vertex at origin and the axis along the positive

y-axis is:

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Class XII Chapter 9 – Differential Equations Maths

Differentiating equation (1) with respect to x, we get:

Dividing equation (2) by equation (1), we get:

This is the required differential equation.

Question 8:

Form the differential equation of the family of ellipses having foci on y-axis and centre at

origin.

Answer

The equation of the family of ellipses having foci on the y-axis and the centre at origin is

as follows:

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Class XII Chapter 9 – Differential Equations Maths

Differentiating equation (1) with respect to x, we get:

Again, differentiating with respect to x, we get:

Substituting this value in equation (2), we get:

This is the required differential equation.

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Class XII Chapter 9 – Differential Equations Maths

Question 9:

Form the differential equation of the family of hyperbolas having foci on x-axis and

centre at origin.

Answer

The equation of the family of hyperbolas with the centre at origin and foci along the x-

axis is:

Differentiating both sides of equation (1) with respect to x, we get:

Again, differentiating both sides with respect to x, we get:

Substituting the value of in equation (2), we get:

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Class XII Chapter 9 – Differential Equations Maths

This is the required differential equation.

Question 10:

Form the differential equation of the family of circles having centre on y-axis and radius

3 units.

Answer

Let the centre of the circle on y-axis be (0, b).

The differential equation of the family of circles with centre at (0, b) and radius 3 is as

follows:

Differentiating equation (1) with respect to x, we get:

Substituting the value of (y – b) in equation (1), we get:

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Class XII Chapter 9 – Differential Equations Maths

This is the required differential equation. as the general solution?

Question 11:

Which of the following differential equations has

A.

B.

C.

D.

Answer

The given equation is:

Differentiating with respect to x, we get:

Again, differentiating with respect to x, we get:

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Class XII Chapter 9 – Differential Equations Maths

This is the required differential equation of the given equation of curve.

Hence, the correct answer is B.

Question 12: as one of its particular solution?

Which of the following differential equation has

A.

B.

C.

D.

Answer

The given equation of curve is y = x.

Differentiating with respect to x, we get:

Again, differentiating with respect to x, we get:

Now, on substituting the values of y, from equation (1) and (2) in each of

the given alternatives, we find that only the differential equation given in alternative C is

correct.

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Class XII Chapter 9 – Differential Equations Maths

Hence, the correct answer is C.

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Class XII Chapter 9 – Differential Equations Maths

Question 1: Exercise 9.4

Answer

The given differential equation is:

Now, integrating both sides of this equation, we get:

This is the required general solution of the given differential equation.

Question 2:

Answer

The given differential equation is:

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Class XII Chapter 9 – Differential Equations Maths

Now, integrating both sides of this equation, we get:

This is the required general solution of the given differential equation.

Question 3:

Answer

The given differential equation is:

Now, integrating both sides, we get:

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Class XII Chapter 9 – Differential Equations Maths

This is the required general solution of the given differential equation.

Question 4:

Answer

The given differential equation is:

Integrating both sides of this equation, we get:

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Class XII Chapter 9 – Differential Equations Maths

Substituting these values in equation (1), we get:

This is the required general solution of the given differential equation.

Question 5:

Answer

The given differential equation is:

Integrating both sides of this equation, we get:

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Class XII Chapter 9 – Differential Equations Maths

Let (ex + e–x) = t.

Differentiating both sides with respect to x, we get:

Substituting this value in equation (1), we get:

This is the required general solution of the given differential equation.

Question 6:

Answer

The given differential equation is:

Integrating both sides of this equation, we get:

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Class XII Chapter 9 – Differential Equations Maths

This is the required general solution of the given differential equation.

Question 7:

Answer

The given differential equation is:

Integrating both sides, we get:

Substituting this value in equation (1), we get:

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Class XII Chapter 9 – Differential Equations Maths

This is the required general solution of the given differential equation.

Question 8:

Answer

The given differential equation is:

Integrating both sides, we get:

This is the required general solution of the given differential equation.

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Class XII Chapter 9 – Differential Equations Maths

Question 9:

Answer

The given differential equation is:

Integrating both sides, we get:

Substituting this value in equation (1), we get:

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Class XII Chapter 9 – Differential Equations Maths

This is the required general solution of the given differential equation.

Question 10:

Answer

The given differential equation is:

Integrating both sides, we get:

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Class XII Chapter 9 – Differential Equations Maths

Substituting the values of in equation (1), we get:

This is the required general solution of the given differential equation.

Question 11:

Answer

The given differential equation is:

Integrating both sides, we get:

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Class XII Chapter 9 – Differential Equations Maths

Comparing the coefficients of x2 and x, we get:

A+B=2

B+C=1

A+C=0

Solving these equations, we get:

Substituting the values of A, B, and C in equation (2), we get:

Therefore, equation (1) becomes:

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Class XII Chapter 9 – Differential Equations Maths

Substituting C = 1 in equation (3), we get:

Question 12:

Answer

Integrating both sides, we get:

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Class XII Chapter 9 – Differential Equations Maths

Comparing the coefficients of x2, x, and constant, we get:

Solving these equations, we get

Substituting the values of A, B, and C in equation (2), we get:

Therefore, equation (1) becomes:

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Class XII Chapter 9 – Differential Equations Maths

Substituting the value of k2 in equation (3), we get:

Question 13:

Answer

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Class XII Chapter 9 – Differential Equations Maths

Integrating both sides, we get:

Substituting C = 1 in equation (1), we get:

Question 14:

Answer

Integrating both sides, we get:

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Class XII Chapter 9 – Differential Equations Maths

Substituting C = 1 in equation (1), we get:

y = sec x

Question 15:

Find the equation of a curve passing through the point (0, 0) and whose differential

equation is .

Answer

The differential equation of the curve is:

Integrating both sides, we get:

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Class XII Chapter 9 – Differential Equations Maths

Substituting this value in equation (1), we get:

Now, the curve passes through point (0, 0).

Substituting in equation (2), we get:

Hence, the required equation of the curve is

Question 16:

For the differential equation find the solution curve passing

through the point (1, –1).

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