Real and Imaginary parts MCQ Quiz - Objective Question with Answer for Real and Imaginary parts - Download Free PDF
Last updated on May 20, 2025
Latest Real and Imaginary parts MCQ Objective Questions
Real and Imaginary parts Question 1:
What is the value of
Answer (Detailed Solution Below)
Real and Imaginary parts Question 1 Detailed Solution
Formula Used:
(a + b) (a - b) = a2 - b2
i2 = -1
Calculation:
Let x =
Squaring both sides,
x2 =
x2 =
x2 =
x2 =
x2 =
x =
Real and Imaginary parts Question 2:
If α and β are the roots of the equation 2z2 – 3z – 2i = 0, where
Answer (Detailed Solution Below)
Real and Imaginary parts Question 2 Detailed Solution
Calculation
2z2 - 32 - 2i = 0
⇒
⇒
⇒
⇒
⇒
⇒
Similarly
⇒
⇒
Real =
Im = 9
Hence option 4 is correct
Real and Imaginary parts Question 3:
If |z1| = |z2| = ....|zn| = 1, then the value of |z1 + z2 + .... zn| -
Answer (Detailed Solution Below)
Real and Imaginary parts Question 3 Detailed Solution
Answer (1)
⇒
∴
=
Real and Imaginary parts Question 4:
If a complex number
Answer (Detailed Solution Below)
Real and Imaginary parts Question 4 Detailed Solution
Calculation
Given:
A complex number
Let
Since
⇒
⇒
⇒
This is the equation of a circle with center
The area of the region bounded by this circle and lying in the first quadrant is
Area of the circle is
The area in the first quadrant is
Hence option 2 is correct
Real and Imaginary parts Question 5:
Let z̅ denote the complex conjugate of a complex number z. If z is a non-zero complex number for which both real and imaginary parts of
Answer (Detailed Solution Below)
Real and Imaginary parts Question 5 Detailed Solution
Calculation
Let z = r.eiθ
So,
So,
For
We get
Hence option 1 is correct
Top Real and Imaginary parts MCQ Objective Questions
If (2 - i) (x - iy) = 3 + 4i then 5x is
Answer (Detailed Solution Below)
Real and Imaginary parts Question 6 Detailed Solution
Download Solution PDFConcept:
Equality of complex numbers.
Two complex numbers z1 = x1 + iy1 and z2 = x2 + iy2 are equal if and only if x1 = x2 and y1 = y2
"OR"
Re (z1) = Re (z2) and Im (z1) = Im (z2).
Calculation:
Given:
(2 - i) (x - iy) = 3 + 4i
⇒ 2x - 2iy - ix + i2y = 3 + 4i
⇒ 2x - 2iy - ix - y = 3 + 4i (∵ i2 = -1)
⇒ (2x – y) + i(-x - 2y) = 3 + 4i
Equating real and imaginary parts,
2x - y = 3 ----(1)
-x - 2y = 4 ----(2)
Solving equation 1 and 2, we get
x =
Now, the value of 5x can be calculated as:
5x = 5 ×
What is the real part of (sin x + icos x)3
Answer (Detailed Solution Below)
Real and Imaginary parts Question 7 Detailed Solution
Download Solution PDFConcept:
Euler's Formula on Complex Numbers:
- eix = cos x + i sin x
- e-ix = cos x - i sin x
Calculation:
(sin x + icos x)3
Take i common, we get
(sin x + icos x)3
=
= -i × (-i sin x + cos x)3
(∵ i3 = -i and 1/i = -i)
= -i × (cos x - i sin x) 3
(∵e-ix = cos x - i sin x)
= -i (cos 3x – i sin 3x)
= (-i cos 3x + i2 sin 3x)
= -sin3x – i cos 3x
∴ Real part = -sin 3x
Find the value of θ for which
Answer (Detailed Solution Below)
Real and Imaginary parts Question 8 Detailed Solution
Download Solution PDFConcept:
Let z = x + iy be a complex number, Where x is called the real part of a complex number or Re (z) and y is called the imaginary part of the complex number or Im (z)
Condition for purely real: Imaginary part equals zero.
Condition for purely imaginary: Real part equals zero.
Calculation:
Multiplying the numerator and denominator by 2 + i sin θ
The imaginary part of z
For z to be purely real Im(z) = 0
⇒ sin θ = 0
So, θ = nπ, where n belongs to an integer
Find the argument of the complex no
Answer (Detailed Solution Below)
Real and Imaginary parts Question 9 Detailed Solution
Download Solution PDFConcept:
Let z = x + iy be a complex number.
- Modulus of z =
- Arg (z) = Arg (x + iy) =
Calculation:
Let
Multiplying numerator and denominator by 1 + i
= 5 + 5i
Hence, option 4 is correct.
If a complex number z = (2x - 3y) + i(x2 - y2) = 0, then Re{z} = ?
Answer (Detailed Solution Below)
Real and Imaginary parts Question 10 Detailed Solution
Download Solution PDFConcept:
Complex Numbers:
- A complex number is a number of the form a + ib, where a and b are real numbers and i is the complex unit defined by i =
. - 'a' is called the real part Re{z} and b is called the imaginary part Im{z}.
- If z1 = z2, then Re{z1} = Re{z2} and Im{z1} = Im{z2}.
- The number 0 can be written as: 0 + i0.
Calculation:
Since, z = (2x - 3y) + i(x2 - y2) = 0, it means that both the real and the imaginary parts of the z are equal to 0.
i.e. Re{z} = 2x - 3y = 0.
If 2x2 + (x2 - y)i = (8 - 3i), find the values of x and y
Answer (Detailed Solution Below)
Real and Imaginary parts Question 11 Detailed Solution
Download Solution PDFConcept:
Equality of complex numbers:
Two complex numbers z1 = x1 + iy1 and z2 = x2 + iy2 are equal if and only if x1 = x2 and y1 = y2
Or Re (z1) = Re (z2) and Im (z1) = Im (z2)
Calculation:
Given that, 2x2 + (x2 - y)i = (8 - 3i)
Comparing the real and imaginary parts,
⇒ 2x2 = 8
⇒ x2 = 4
⇒ x = -2, 2
And, x2 - y = -3
⇒ 4 - y = -3 [∵ x2 = 4]
⇒ y = 7
Hence, option (3) is correct.
Find the real and imaginary part of the complex number
Answer (Detailed Solution Below)
Real and Imaginary parts Question 12 Detailed Solution
Download Solution PDFConcept:
Equality of complex numbers.
Two complex numbers z1 = x1 + iy1 and z2 = x2 + iy2 are equal if and only if x1 = x2 and y1 = y2
Or Re (z1) = Re (z2) and Im (z1) = Im (z2).
Calculations:
Multiplying numerator and denominator by i
Re(z) = -1
Im(z) = -1
Hence , option 4 is correct
If
Answer (Detailed Solution Below)
Real and Imaginary parts Question 13 Detailed Solution
Download Solution PDFConcept:
Equality of complex numbers.
Two complex numbers z1 = x1 + iy1 and z2 = x2 + iy2 are equal if and only if x1 = x2 and y1 = y2
Or Re (z1) = Re (z2) and Im (z1) = Im (z2).
Calculations:
Given:
As we know i2 = -1
Comparing real and imaginary parts, we get.
1. The difference of Z and its conjugate is an imaginary number.
2. The sum of Z and its conjugate is a real number.
Answer (Detailed Solution Below)
Real and Imaginary parts Question 14 Detailed Solution
Download Solution PDFConcept:
Let z = x + iy be a complex number,
Where x is called the real part of the complex number or Re (z) and y is called the Imaginary part of the complex number or Im (z)
Conjugate of z = z̅ = x - iy
Calculation:
1. The difference of Z and its conjugate is an imaginary number.
Consider z = a + ib ....(i)
conjugate of z = z̅ = a - ib ....(ii)
eq(i) - eq (ii)
z - z̅ = a + ib - a + ib
⇒ 2ib
Thus it is clear that the difference of z and its conjugate is an imaginary number.
2. The sum of Z and its conjugate is a real number.
eq (i) + eq(ii)
z + z̅ = a + ib + a - ib
⇒ 2a
Thus it is clear that the sum of Z and its conjugate is a real number.
So, Both 1 and 2 are correct.
If
Answer (Detailed Solution Below)
Real and Imaginary parts Question 15 Detailed Solution
Download Solution PDFConcept:
Let A = x1 + iy1 and B = x2 + iy2
If A = B then x1 = x2 and y1 = y2
Calculations:
Given
⇒
⇒
We know i2 = -1
⇒
⇒
⇒A + iB = 2i
⇒ A + iB = 0 + 2i
Comparing real and imaginary parts, we get.
⇒A = 0