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📐 Mathematics  ·  Complex Numbers and Quadratic Equations  ·  JEE

If z = (√3 + i)/(1 - i), find |z| and arg(z).

Answer: |z|=√2, arg=5π/12.

  • A |z|=√2, arg=5π/12
  • B |z|=√2, arg=7π/12
  • C |z|=2, arg=5π/12
  • D |z|=1, arg=5π/12

Correct answer: A. |z|=√2, arg=5π/12

Explanation: |z| = |sqrt(3)+i|/|1-i| = 2/sqrt(2) = sqrt(2). arg(numerator) = pi/6; arg(denominator) = -pi/4. arg(z) = pi/6 - (-pi/4) = pi/6 + pi/4 = 2pi/12+3pi/12 = 5pi/12.

Argand Plane: z = a + ibReImz = a+iba (real part)b (imaginary part)θ = arg(z)|z| = length of the vector OZ = √(a²+b²); θ = angle OZ makes with the positive real axis

A complex number z = a+ib is plotted as a point (or vector from the origin) on the Argand plane, with the real part along the horizontal axis and the imaginary part along the vertical; its modulus |z| is the vector's length, and its argument θ is the angle from the positive real axis.

Concept context

Complex numbers in a+ib form, modulus, argument, polar form, cube roots of unity, and quadratic equations with complex roots

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