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JEE Main201910 Apr 2019Evening ShiftMathematicsComplex NumberActual

If z and ω are two complex numbers such that z ω = 1 and a r g z - a r g ( ω ) = π 2 , then:

Options

  1. Az ω ¯ = 1 - i 2
  2. Bz ¯ ω = i
  3. Cz ω ¯ = - 1 + i 2
  4. Dz ¯ ω = - i

Correct answer

D. z ¯ ω = - i

Step-by-step solution

Let z = r and a r g z = θ , given a r g z - a r g ω = π 2 ⇒ θ - a r g ω = π 2 ⇒ a r g ω = θ - π 2 We know that, if z = r   &   a r g z = θ then 1 z = 1 r   &   a r g z ¯ = - a r g z = - θ , Hence, ω = 1 r and a r g ( ω ¯ ) = - a r g ω = π 2 - θ Now, by using Euler form i.e. if z = r   &   a r g z = θ , then z = r e i θ , we have z = r e i θ and ω = 1 r e

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