Join WhatsApp Icon JEE WhatsApp Group
Question 81

Let $$z = 1 + i$$ and $$z_1 = \frac{1 + i\bar{z}}{\bar{z}(1-z) + \frac{1}{z}}$$. Then $$\frac{12}{\pi} \arg z_1$$ is equal to


Correct Answer: 9

We are given $$z = 1 + i$$ and asked to find $$\frac{12}{\pi}\arg(z_1)$$ where $$z_1 = \frac{1 + i\bar{z}}{\bar{z}(1-z) + \frac{1}{z}}$$. To begin, we note that $$\bar{z} = 1 - i$$, so $$1 + i\bar{z} = 1 + i(1 - i) = 1 + i - i^2 = 1 + i + 1 = 2 + i$$.

Next, we calculate the denominator. First, $$\bar{z}(1 - z) = (1 - i)(1 - 1 - i) = (1 - i)(-i) = -i + i^2 = -1 - i$$, and $$\frac{1}{z} = \frac{1}{1 + i} = \frac{1 - i}{2}$$. Adding these gives $$-1 - i + \frac{1 - i}{2} = \frac{-2 - 2i + 1 - i}{2} = \frac{-1 - 3i}{2}$$.

Therefore, $$z_1 = \frac{2 + i}{\frac{-1 - 3i}{2}} = \frac{2(2 + i)}{-1 - 3i} = \frac{4 + 2i}{-1 - 3i}$$. Multiplying numerator and denominator by the conjugate of the denominator yields $$z_1 = \frac{(4 + 2i)(-1 + 3i)}{(-1 - 3i)(-1 + 3i)} = \frac{-4 + 12i - 2i + 6i^2}{1 + 9} = \frac{-4 + 10i - 6}{10} = \frac{-10 + 10i}{10} = -1 + i\,. $$

Since $$\arg(-1 + i) = \pi - \frac{\pi}{4} = \frac{3\pi}{4}$$, it follows that $$\frac{12}{\pi} \times \frac{3\pi}{4} = \frac{12 \times 3}{4} = 9$$. Thus, the answer is $$\boxed{9}$$.

Get AI Help

Video Solution

video

Create a FREE account and get:

  • Free JEE Mains Previous Papers PDF
  • Take JEE Mains paper tests

JEE Quant Questions | JEE Quantitative Ability

JEE DILR Questions | LRDI Questions For JEE

JEE Verbal Ability Questions | VARC Questions For JEE

Free JEE Topicwise Questions

JEE Rotational MotionJEE Units & MeasurementsJEE Atomic StructureJEE GravitationJEE Periodic Table & PeriodicityJEE StatisticsJEE Inverse Trigonometric FunctionsJEE Magnetism & Magnetic MaterialsJEE Sequences & SeriesJEE MatricesJEE Alternating CurrentsJEE Carboxylic AcidsJEE Permutations & CombinationsJEE Work, Energy & PowerJEE Electromagnetic InductionJEE Electronic DevicesJEE d and f-Block ElementsJEE Chemical KineticsJEE Heat TransferJEE Three Dimensional GeometryJEE Magnetic Effects of CurrentJEE Hydrocarbons - AromaticJEE Electromagnetic WavesJEE Aldehydes & KetonesJEE Hydrocarbons - AlkanesJEE Applications of DerivativesJEE EquilibriumJEE Indefinite IntegrationJEE Chemical ThermodynamicsJEE ElectrochemistryJEE ProbabilityJEE BiomoleculesJEE Continuity & DifferentiabilityJEE Kinetic Theory of GasesJEE Vector AlgebraJEE Hydrocarbons - AlkynesJEE Differential EquationsJEE Current & ResistanceJEE Straight LinesJEE WavesJEE Redox ReactionsJEE Hydrocarbons - AlkenesJEE DeterminantsJEE SolutionsJEE Ray OpticsJEE Dual Nature of Matter & RadiationJEE Chemical Bonding & Molecular StructureJEE Complex NumbersJEE Sets, Relations & FunctionsJEE Electric Charges & FieldsJEE Laws of MotionJEE Fluid MechanicsJEE Basic Concepts in ChemistryJEE Trigonometric FunctionsJEE LimitsJEE Laws of ThermodynamicsJEE Kinematics - 2D MotionJEE p-Block Elements (Groups 13-18)JEE Simple Harmonic MotionJEE Electric Potential & CapacitanceJEE Coordination CompoundsJEE JEE 2D GeometryJEE CirclesJEE Definite IntegrationJEE EMF & Circuit AnalysisJEE Surface TensionJEE Atoms & NucleiJEE Laboratory Experiments - XIJEE Number SystemJEE Basic Principles of Organic ChemistryJEE Wave OpticsJEE Quadratic EquationsJEE Alcohols, Phenols & EthersJEE Organic Compounds with HalogensJEE DifferentiationJEE Conic SectionsJEE Nitrogen-Containing CompoundsJEE ElasticityJEE Practical Organic ChemistryJEE Kinematics - 1D MotionJEE Purification & CharacterisationJEE Binomial Theorem
Ask AI