For any two complex numbers z1 and z2, prove that Re (z1z2) = Re z1 Re z2-Im z1 Im z2.
Solution and Explanation
Let z1=x1+iy1 and z2=x2+iy2
∴ z1z2=(x1+iy1) (x2+iy2)
= x1(x2+iy2)+iy1(x2+iy2)
= x1x2+ix1y2+iy1x2+i2y1y2
= x1x2+ix1y2+iy1x2--y1y2 [i2=-1]
⇒ (x1x2-y1y2)+i(x1y2+y1x2)
⇒ Re(z1z2)=Re z1Re Z2-Imz1 ImZ2
Hence, proved.
Top Questions on Algebra of Complex Numbers
- Let \( \alpha, \beta \in \mathbb{N} \) be roots of the equation \( x^2 - 70x + \lambda = 0 \), where \( \frac{\lambda}{2}, \frac{\lambda}{3} \notin \mathbb{N} \). If \( \lambda \) assumes the minimum possible value, then \[ \frac{\left( \sqrt{\alpha - 1} + \sqrt{\beta - 1} \right)(\lambda + 35)}{|\alpha - \beta|} \] is equal to____.
- JEE Main - 2024
- Mathematics
- Algebra of Complex Numbers
- If \( z \) is a complex number, then the number of common roots of the equation \( z^{1985} + z^{100} + 1 = 0 \) and \( z^3 + 2z^2 + 2z + 1 = 0 \), is equal to:
- JEE Main - 2024
- Mathematics
- Algebra of Complex Numbers
- \(z_1^3+z_2^3=20+15i\) then \(|z_1^4+z_2^4|\) is equal to
- JEE Main - 2024
- Mathematics
- Algebra of Complex Numbers
- If \( \alpha \) is a root of the equation \( x^2 - x + 1 = 0 \), then \(\left(\alpha + \frac{1}{\alpha}\right)^3 + \left(\alpha^2 + \frac{1}{\alpha^2}\right)^3 + \left(\alpha^3 + \frac{1}{\alpha^3}\right)^3 + \left(\alpha^4 + \frac{1}{\alpha^4}\right)^3 =\)
- TS EAMCET - 2024
- Mathematics
- Algebra of Complex Numbers
- If the expression \( 7 + 6x - 3x^2 \) attains its extreme value \( \beta \) at \( x = \alpha \), then the sum of the squares of the roots of the equation \( x^2 + ax - \beta = 0 \) is:
- TS EAMCET - 2024
- Mathematics
- Algebra of Complex Numbers
Questions Asked in CBSE Class XI exam
- Consider the reactions:
- H3PO2(aq) + 4 AgNO3(aq) + 2 H2O(l) \(\rightarrow\) H3PO4(aq) + 4Ag(s) + 4HNO3(aq)
- H3PO2(aq) + 2CuSO4(aq) + 2 H2O(l) \(\rightarrow\) H3PO4(aq) + 2Cu(s) + H2SO4(aq)
- C6H5CHO(l) + 2[Ag (NH3)2]+(aq) + 3OH- (aq) \(\rightarrow\) C6H5COO- (aq) + 2Ag(s) + 4NH3(aq) + 2 H2O(l)
- C6H5CHO(l) + 2Cu2+(aq) + 5OH-(aq) \(\rightarrow\) No change observed.
What inference do you draw about the behaviour of Ag+ and Cu2+ from these reactions?
- CBSE Class XI
- Redox Reactions In Terms Of Electron Transfer Reactions
- Find \((x + 1)^6 - (x - 1)^6\). Hence or otherwise evaluate \((\sqrt2 + 1)^6 + (\sqrt2 - 1)^6.\)
- CBSE Class XI
- Binomial Theorem for Positive Integral Indices
- If U = {a, b, c, d, e, f, g, h}, find the complements of the following sets:
(i) A = {a, b, c}
(ii) B = {d, e, f, g}
(iii) C = {a, c, e, g}
(iv) D = {f, g, h, a}- CBSE Class XI
- Complement of a Set
- Consider the following species: N3- , O2-, F-, Na+, Mg2+ and Al3+
- What is common in them?
- Arrange them in the order of increasing ionic radii.
- CBSE Class XI
- Modern Periodic Law And The Present Form Of The Periodic Table
- Find and write down structures of 10 interesting small molecular weight biomolecules. Find if there is any industry which manufactures the compounds by isolation. Find out who are the buyers.
- CBSE Class XI
- How To Analyse Chemical Composition?
Concepts Used:
Complex Number
A Complex Number is written in the form
a + ib
where,
- “a” is a real number
- “b” is an imaginary number
The Complex Number consists of a symbol “i” which satisfies the condition i^2 = −1. Complex Numbers are mentioned as the extension of one-dimensional number lines. In a complex plane, a Complex Number indicated as a + bi is usually represented in the form of the point (a, b). We have to pay attention that a Complex Number with absolutely no real part, such as – i, -5i, etc, is called purely imaginary. Also, a Complex Number with perfectly no imaginary part is known as a real number.