Home
Class 12
MATHS
Consider the following in respect of a ...

Consider the following in respect of a complex number Z :
1. `bar((Z^(-1)))=(barZ)^(-1)`
2. `Z Z^(-1) =|Z|^(2)`
Which of the above is/are correct?

A

`1` only

B

`2` only

C

Both `1` and `2`

D

Neither `1` nor `2`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the two statements regarding the complex number \( Z \). ### Step 1: Analyze the first statement The first statement is: \[ \overline{(Z^{-1})} = (\overline{Z})^{-1} \] **Solution:** 1. Let \( Z = a + i b \), where \( a \) and \( b \) are real numbers. 2. The conjugate of \( Z \) is: \[ \overline{Z} = a - i b \] 3. The inverse of \( Z \) is given by: \[ Z^{-1} = \frac{\overline{Z}}{|Z|^2} = \frac{a - i b}{a^2 + b^2} \] 4. Now, find the conjugate of \( Z^{-1} \): \[ \overline{(Z^{-1})} = \overline{\left(\frac{a - i b}{a^2 + b^2}\right)} = \frac{\overline{(a - i b)}}{|Z|^2} = \frac{a + i b}{a^2 + b^2} \] 5. Now, calculate \( (\overline{Z})^{-1} \): \[ (\overline{Z})^{-1} = \frac{Z}{|Z|^2} = \frac{a + i b}{a^2 + b^2} \] 6. Since both expressions are equal: \[ \overline{(Z^{-1})} = (\overline{Z})^{-1} \] This statement is **true**. ### Step 2: Analyze the second statement The second statement is: \[ Z Z^{-1} = |Z|^2 \] **Solution:** 1. We already know that \( Z^{-1} = \frac{\overline{Z}}{|Z|^2} \). 2. Now, calculate \( Z Z^{-1} \): \[ Z Z^{-1} = Z \cdot \frac{\overline{Z}}{|Z|^2} = \frac{Z \overline{Z}}{|Z|^2} \] 3. Since \( Z \overline{Z} = |Z|^2 \), we have: \[ Z Z^{-1} = \frac{|Z|^2}{|Z|^2} = 1 \] 4. Therefore, the statement \( Z Z^{-1} = |Z|^2 \) is **false** because \( Z Z^{-1} = 1 \). ### Conclusion - The first statement is true. - The second statement is false. Thus, the correct answer is that only the first statement is correct.
Promotional Banner

Topper's Solved these Questions

  • PROPERTIES OF TRIANGLE, INVERSE TRIGONOMETRIC FUNCTION

    NDA PREVIOUS YEARS|Exercise MCQ|103 Videos
  • QUESTION PAPER 2021(I)

    NDA PREVIOUS YEARS|Exercise MULTIPLE CHOICE QUESTION|108 Videos

Similar Questions

Explore conceptually related problems

If z is a nonzero complex number then (bar(z^-1))=(barz)^-1 .

Let C be the set of complex number and z_(1),z_(2) are in C. 1. agr (z_(1))=agr(z_(2))impliesz_(1)=z_(2) 2. |z_(1)|=|z_(2)|impliesz_(1)=z_(2) Which of the statements givben above is/are correct?

If z_(1),z_(2) are any two complex numbers such that |z_(1)+z_(2)|=|z_(1)|+z_(2)|, which one of the following is correct ?

Number of complex numbers such that |z| = 1 and z = 1 - 2 bar(z) is

Let z_(1),z_(2) and z_(3) be non-zero complex numbers satisfying z^(2)=bar(iz), where i=sqrt(-1). Consider the following statements: 1. z_(1)z_(2)z_(3) is purely imaginary. 2. z_(1)z_(2)+z_(2)z_(3)+z_(3)z_(1) is purely real. Which of the above statements is/are correct?

For two complex numbers z_(1) and z_(2) , we have |(z_(1)-z_(2))/(1-barz_(1)z_(2))|=1 , then

If z_(1) and z_(2) are two complex numbers such that |(z_(1)-z_(2))/(1-barz_(1)z_(2))|=1 , then which one of the following is true?

Numbers of complex numbers z, such that abs(z)=1 and abs((z)/bar(z)+bar(z)/(z))=1 is

NDA PREVIOUS YEARS-QUESTION PAPER 2021-MULTIPLE CHOICE QUESTIONS
  1. Let R be a relation defined as xRy if and only if 2x+3y = 20, where x...

    Text Solution

    |

  2. Consider the following statements : 1. A function f:Z to Z, defi...

    Text Solution

    |

  3. Consider the following in respect of a complex number Z : 1. bar((...

    Text Solution

    |

  4. Consider the following statements in respect of an arbitrary complex ...

    Text Solution

    |

  5. What is the modulus of the complex number i^(2n+1) (-i)^(2n-1), wher...

    Text Solution

    |

  6. If alpha and beta are the roots of the equation 4x^(2)+2x-1=0, then wh...

    Text Solution

    |

  7. If one root of the polynomial f(x)=5x^2+13 x+k is reciprocal of the ot...

    Text Solution

    |

  8. In how many ways can a team of 5 players be selected from 8 players s...

    Text Solution

    |

  9. What is the coefficient of the middle term in the expansion of (1+4x+...

    Text Solution

    |

  10. If tan x= -(3)/(4) and x is in the second quadrant, then what is the...

    Text Solution

    |

  11. What is the value of the following? "cosec" ((7pi)/(6)) sec ((5pi)/...

    Text Solution

    |

  12. If the determinant |(x, 1, 3),(0, 0,1),(1, x, 4)|=0 then what is x...

    Text Solution

    |

  13. What is the value of the following? tan 31^(@) tan 33^(@) tan 35^(@)...

    Text Solution

    |

  14. If f(x) =|(1, x, x+1),(2x, x(x-1), x(x+1)), (3x(x-1), 2(x-1)(x-2), x(x...

    Text Solution

    |

  15. If sin^-1x-cos^-1x=pi/6 then x=

    Text Solution

    |

  16. What is the values of the following? ( sin 24^(@) +cos 66^(@)) (sin...

    Text Solution

    |

  17. A chord subtends an angle 120^(@) at the centre of the circle of radiu...

    Text Solution

    |

  18. Prove that (1+cot theta - "cosec" theta )(1+ tan theta +sec theta )...

    Text Solution

    |

  19. What is (1+ tan^(2) theta)/(1+cot^(2) theta) -((1-tan theta)/(1-cot t...

    Text Solution

    |

  20. What is the interior angle of a regular octagon of side length 2 cm?

    Text Solution

    |