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Published on: 21/10/2025
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1.
Find the modulus of \(\frac { 1+i }{ 1-i } -\frac { 1-i }{ 1+i } \)
2.
If x + iy = \(\frac { a+ib }{ a-ib } \) prove that x2 + y2 = 1.
3.
Find the conjugate of \(\frac { (3-2i)(2+3i) }{ (1+2i)(2-i) }\)
4.
Find the number of non-zero integral solutions of the equation \(\left| 1-i \right| ^{ x }\) = 2x .
5.
If \(x+iy=\frac{(a+i)^2}{2a-i}\) show that \(x^2+y^2=\frac{(a^2+1^2)}{4a^2+1}.\)
6.
If z1 = 3+5i and z2 = -3i, then verify that \(\overset { \_ \_ \_ \_ }{ \left( \frac { { z }_{ 1 } }{ { z }_{ 2 } } \right) } =\frac { { \overset { \_ }{ z } }_{ 1 } }{ { \overset { \_ }{ z } }_{ 2 } } \)
7.
Convert the complex number \(-\sqrt { 3 } -i\) into polar form and determine the modulus and the principal value of the argument of given complex number.
8.
If \({ \left( \frac { 1+i }{ 1-i } \right) }^{ 3 }-{ \left( \frac { 1-i }{ 1+i } \right) }^{ 3 }=x+iy\), then find (x,y).
9.
Express (5 – 3i)3 in the form a + ib.
10.
If 4x + i (3x – y) = 3 + i (– 6), where x and y are real numbers, then find the values of x and y.
11.
If z1 = 2-i, z2 = 1+i find \(\left| \frac { { z }_{ 1 }+{ z }_{ 2 }+1 }{ { z }_{ 1 }-{ z }_{ 2 }+1 } \right| \)
12.
Find the multiplicative inverse of each of the complex numbers given in the Exercises : -i
13.
Find the multiplicative inverse of each of the complex numbers given in the Exercises : \(\sqrt { 5 } \)+3i
14.
Find the multiplicative inverse of each of the complex numbers given in the Exercises: 4-3i
15.
If a + ib = c + id, then _______.
\(a^{2}+c^{2}=0\)
\(b^{2}+c^{2}=0\)
\(b^{2}+d^{2}=0\)
\(a^{2}+b^{2}=c^{2}+d^{2}\)
16.
Which of the following are correct?
\(\text { I. }|3+i|=\sqrt{10} ;|2-5 i|=\sqrt{29}\)
\(\text { II. }(\overline{3+i})=3-i ;(\overline{2-5 i})=2+5 i \text { and }(-\overline{3 i-5})=3 i-5\)
\(\text { III. } z^{-1}=\frac{\bar{z}}{|z|^{2}} \text { or } Z \bar{z}=|z|^{2}, z \neq 0\)
I and III are correct
I and II are correct
All are correct
None of these
17.
If z = i39, then simplest form of z is equal to _______.
1+ 0i
0+ i
0+ 0i
1+ i
18.
If Z is a complex number and z + (-z) = 0, then _______.
(-z) is called additive inverse of z
-z is additive identity of z
= z is closure of z
-z is commutative of z
19.
If 4x + i(3x - y) =3 + i(-6), where x and y are real numbers, then the values of x and y are _____.
x = 3,y = 4
\(x=\frac{3}{4}, y=\frac{33}{4}\)
x = 4,y = 3
x = 33,y = 4
20.
Which of the following options define 'imaginary number'?
Square root of any number
Square root of positive number
Square root of negative number
Cube root of number
1.
\(\left| \frac { 1+i }{ 1-i } -\frac { 1-i }{ 1-i } \right| =\left| \frac { (1+i)^{ 2 }-(1-i)^{ 2 } }{ (1-i)((1+i) } \right| \)
= \(\left| \frac { 1+{ i }^{ 2 }+2i-1-{ i }^{ 2 }+2i }{ 1-{ i }^{ 2 } } \right| \)
= \(\left| \frac { 4i }{ 2 } \right| =|2i|=\sqrt { 4 } =2\)
2.
We have,
\(x+i y=\frac{(a+i b)(a+i b)}{(a-i b)(a+i b)}=\frac{a^{2}-b^{2}+2 a b i}{a^{2}+b^{2}}=\frac{a^{2}-b^{2}}{a^{2}+b^{2}}+\frac{2 a b}{a^{2}+b^{2}} i\)
So that, \(x-i y=\frac{a^{2}-b^{2}}{a^{2}+b^{2}}-\frac{2 a b}{a^{2}+b^{2}} i\)
Therefore,
\(x^{2}+y^{2}=(x+i y)(x-i y)=\frac{\left(a^{2}-b^{2}\right)^{2}}{\left(a^{2}+b^{2}\right)^{2}}+\frac{4 a^{2} b^{2}}{\left(a^{2}+b^{2}\right)^{2}}=\frac{\left(a^{2}+b^{2}\right)^{2}}{\left(a^{2}+b^{2}\right)^{2}}=1\)
3.
We have, \(\frac{(3-2 i)(2+3 i)}{(1+2 i)(2-i)}\)
\( =\frac{6+9 i-4 i+6}{2-i+4 i+2}=\frac{12+5 i}{4+3 i} \times \frac{4-3 i}{4-3 i}\)
\( =\frac{48-36 i+20 i+15}{16+9}=\frac{63-16 i}{25}=\frac{63}{25}-\frac{16}{25} i\)
Therefore, conjugate of \(\frac{(3-2 i)(2+3 i)}{(1+2 i)(2-i)}\) is \(\frac{63}{25}+\frac{16}{25} i\).
4.
\(\text { We have, }\left(\sqrt{1^{2}+(-1)^{2}}\right)^{x}=2^{x} \)
\( \Rightarrow \left(\sqrt{1^2+(-1)^2}\right)^{\mathrm{x}}=2^{\mathrm{x}} \ldots \ldots \ldots \ldots|\mathrm{z}|=\sqrt{\mathrm{x}^2+\mathrm{y}^2} \)
\( \Rightarrow (\sqrt{2})^{\mathrm{x}}=2^{\mathrm{x}} \)
\( \Rightarrow 2^{\frac{x}{2}}=2^{\mathrm{x}} \)
\( \Rightarrow \frac{\mathrm{x}}{2}=\mathrm{x} \)
\( \Rightarrow \mathrm{x}=2 \mathrm{x} \)
\( \Rightarrow \mathrm{x}=0
\)
Thus, x=0 is the only integral solution of the given equation.
Therefore, the number of non-zero integral solutions of the given equation is 0.
5.
Here \(x+iy=\frac{(a+i)^2}{2a-i}\).......(i)
Taking conjugate on both sides, we have
\(\overline {x+iy}=\frac{\overline {(a+i)}^2}{\overline {(2a-i)}}\)
\(\Rightarrow =x-iy=\frac{(a-i)^2}{2a+i}\).....(ii)
Multiplying (i) and (ii), we have
\((x+iy)(x-iy)=\frac{(a+i)^2}{2a-i}\times\frac{(a-i)^2}{2a+i}\)
\(\Rightarrow =x^2-i^2y^2=\frac{(a+i)^2(a-i)^2}{4a^2-i^2}\)
\(\Rightarrow =x^2+y^2=\frac{(a^2-i^2)^2}{4a^2+1}\ [\because i^2=-1]\)
\(=\frac{(a^2+1)^2}{4a^2+1}\)
6.
\(Given, { z }_{ 1 }=3+5i\quad and\quad { z }_{ 2 }=2-3i\)
\(Now, \frac { { z }_{ 1 } }{ { z }_{ 2 } } =\frac { 3+5i }{ 2-3i } =\frac { 3+5i }{ 2-3i } \times \frac { 3+5i }{ 2-3i } \)
\([by\quad rationalising\quad the\quad denominator]\)
\(=\frac { 6+9i+10i+15{ i }^{ 2 } }{ 4-9{ i }^{ 2 } } =\frac { 6+19i-15 }{ 4+9 } \quad [\because { i }^{ 2 }=-1]\)
\(=\frac { -9+19i }{ 13 } =\frac { -9 }{ 13 } +\frac { 9 }{ 13 } i\ \quad .....(i)\)
\(\because LHS=\overset { \_ \_ \_ \_ }{ \left( \frac { { z }_{ 1 } }{ { z }_{ 2 } } \right) } =\overset { \_ \_ \_ \_ \_ \_ \_ \_ \_ \_ \_ \_ \_ }{ \left( \frac { -9 }{ 13 } +\frac { 9 }{ 13 } i \right) } =\frac { -9 }{ 13 } -\frac { 9 }{ 13 } i\)
\(Now, consider\quad RHS =\frac { \overset { \_ \_ }{ { z }_{ 1 } } }{ \overset { \_ \_ }{ { z }_{ 2 } } } =\frac { \overset { \_ \_ \_ \_ \_ }{ 3+5i } }{ \overset { \_ \_ \_ \_ \_ \_ }{ 2-3i } } =\frac { 3+5i }{ 2-3i } \)
\(=\frac { 3+5i }{ 2-3i } \times \frac { 2-3i }{ 2-3i } \)
\([by\quad rationalising\quad denominator]\)
\(=\frac { 6-9i-10i+15{ i }^{ 2 } }{ 4-9{ i }^{ 2 } } =\frac { 6-19i-15 }{ 4+9 } \quad [\because { i }^{ 2 }=-1]\)
\(=\frac { -9-19i }{ 13 } =\frac { -9 }{ 13 } -\frac { 9 }{ 13 } i\quad .....(ii)\)
\(From\quad Eqs.(i)\quad and\quad (ii),we\quad get\)
\(\left( \frac { { z }_{ 1 } }{ { z }_{ 2 } } \right) =\frac { \overset { \_ }{ { z }_{ 1 } } }{ \overset { \_ }{ { z }_{ 2 } } } \)
7.
Let z= \(-\sqrt { 3 } -i\) =r( \(cos\theta +isin\theta \) )
On equating real and imaginary parts, we get
\(rcos\theta =-\sqrt { 3 } ...(i)\)
\( rsin\theta =-1 ...\quad (ii)\)
On squaring and adding Eqs. (i) and (ii), we get
\({ r }^{ 2 }{ cos }^{ 2 }\theta +{ r }^{ 2 }{ sin }^{ 2 }\theta =(-\sqrt { 3 } { ) }^{ 2 }+(-1{ ) }^{ 2 }\)
\(\Rightarrow { r }^{ 2 }{ r }^{ 2 }{ cos }^{ 2 }\theta +{ r }^{ 2 }{ sin }^{ 2 }\theta )=3+1\)
\(\Rightarrow { r }^{ 2 }=4\quad [\because { r }^{ 2 }{ cos }^{ 2 }\theta +{ r }^{ 2 }{ sin }^{ 2 }\theta =1]\)
\(\Rightarrow r=2\quad \quad [\because \ r>0]\)
Now, from Eqs. (i) and (ii), we get
\(cos\theta =-\frac { \sqrt { 3 } }{ 2 } and\ sin\theta =-\frac { 1 }{ 2 } \)
\(\Rightarrow tan\theta =\frac { 1 }{ \sqrt { 3 } } \quad [\because tan\theta =\frac { sin\theta }{ cos\theta } ]\)
Now, let
\(tan\alpha =\left| tan\theta \right| ,where\quad 0<\alpha >\frac { \pi }{ 2 } \)
\(\Rightarrow \quad tan\alpha =\frac { 1 }{ \sqrt { 3 } } =tan\frac { \pi }{ 6 } \Rightarrow \alpha =\frac { \pi }{ 6 } \)
Since, z lies in III quadrant.
\(\therefore \ \theta =-\pi +\alpha\)
\(=-\pi +\frac { \pi }{ 6 } =-\frac { 5\pi }{ 6 } \)
So, polar form of z is 2( \(cos(\frac { -5\pi }{ 6 } )+isin(\frac { -5\pi }{ 6 } )\) ).
Hence, modulus of z is 2 and argument of z is \(-\frac { 5\pi }{ 6 } \)
8.
Consider, \(\frac { 1+i }{ 1-i } =\frac { 1+i }{ 1-i } \times \frac { 1+i }{ 1+i } \)
[by rationalising the denominator]
\(=\frac { { \left( 1+i \right) }^{ 2 } }{ 1-{ i }^{ 2 } } =\frac { 1+{ i }^{ 2 }+2i }{ 1+1 }\)
\(\Rightarrow \ \frac { 1+i }{ 1-i } =\frac { 1-1+2i }{ 2 } =i\quad \left[ \because \ { i }^{ 2 }=-1 \right] ...(i)\)
\( Now,\ \frac { 1-i }{ 1+i } =\frac { 1 }{ \left( \frac { 1+i }{ 1-i } \right) } =\frac { 1 }{ i } \)
\(=\frac { 1 }{ i } \times \frac { i }{ i } =\frac { i }{ { i }^{ 2 } } =\frac { i }{ (-1) } =-i\quad \left[ \because \ { i }^{ 2 }=-1 \right] ...(ii)\)
\(Hence,\ { \left( \frac { 1+i }{ 1-i } \right) }^{ 3 }-{ \left( \frac { 1-i }{ 1+i } \right) }^{ 3 }={ i }^{ 3 }-{ \left( -i \right) }^{ 3 }\)
\(={ i }^{ 3 }+{ i }^{ 3 }=2{ i }^{ 3 }=2(-i)=0-2i\ \left[ \because \ { i }^{ 3 }=-i \right] \)
\(\therefore \ x+iy=0-2i\)
On comparing real and imaginary parts on both sides, we get x=0 and y=-2
\(\therefore \) (x,y) = (0,-2)
9.
We have, (5 – 3i)3 = 53 – 3 × 52 × (3i) + 3 × 5 (3i)2 – (3i)3
= 125 – 225i – 135 + 27i = – 10 – 198i.
10.
We have,
4x + i (3x – y) = 3 + i (–6) ... (1)
Equating the real and the imaginary parts of (1), we get
4x = 3, 3x – y = – 6,
which, on solving simultaneously, give \(x=\frac{3}{4}\) and \(y=\frac{33}{4}\)
11.
∴ \(\left| \frac { { z }_{ 1 }+{ z }_{ 2 }+1 }{ { z }_{ 1 }-{ z }_{ 2 }+1 } \right| \)
= \(\left| \frac { 2-i+1+i+1 }{ 2-i-1-i+1 } \right| =\left| \frac { 4 }{ 2-2i } \right| \)
= \(\frac { 4 }{ |2-2i| } =\frac { 4 }{ \sqrt { (2)^{ 2 }+(-2)^{ 2 } } } \)
= \(\frac { 4 }{ \sqrt { 4+4 } } =\frac { 4 }{ \sqrt { 8 } } =\frac { 4 }{ 2\sqrt { 2 } } =\sqrt { 2 } \)
12.
Multiplicative inverse of -i
= \(\frac { 1 }{ -i } =\frac { i }{ -{ i }^{ 2 } } =\frac { 1 }{ -(-1) } =i\)
13.
M.I of \(\sqrt { 5 } \)+3i = \(\frac { 1 }{ \sqrt { 5 } +3i } \)
= \(\frac { 1 }{ \sqrt { 5 } +3i } \times \frac { \sqrt { 5 } -3i }{ \sqrt { 5 } -3i } \)
= \(\frac { \sqrt { 5 } -3i }{ (\sqrt { 5 } )^{ 2 }+(3i)^{ 2 } } =\frac { \sqrt { 5 } -3i }{ 5-9i^{ 2 } } \)
= \(\frac { \sqrt { 5 } -3i }{ 5+9 } \)
\(=\frac{\sqrt{5}}{14}-\frac{3 i}{14}\)
14.
Multiplicative inverse of (4-3i) = \(\frac { 1 }{ 4-3i } =\frac { 1 }{ 4-3i } \times \frac { 4+3i }{ 4+3i } \)
= \(\frac { 4+3i }{ (4)^{ 2 }+(3i)^{ 2 } } =\frac { 4+3i }{ 16-9i^{ 2 } } \)
= \(\frac { 4+3i }{ 16+9 } \)
= \(\frac{4}{25}+\frac{3}{25} i\)
15.
(d)
\(a^{2}+b^{2}=c^{2}+d^{2}\)
16.
(c)
All are correct
17.
(b)
0+ i
18.
(a)
(-z) is called additive inverse of z
19.
(b)
\(x=\frac{3}{4}, y=\frac{33}{4}\)
20.
(c)
Square root of negative number
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