Mathematics · Complex Numbers

JEE Main 2026 — 23 January, Evening Shift — Question 17

If z=32+i2,i=−1\mathrm{z}=\frac{\sqrt{3}}{2}+\frac{\mathrm{i}}{2}, \mathrm{i}=\sqrt{-1}, then (z201−i)8\left(\mathrm{z}^{201}-\mathrm{i}\right)^{8} is equal to

  1. Option A:

    −1-1

  2. Option B:

    00

  3. Option C:

    11

  4. Option D:

    256256

    Correct

Answer: D

Step-by-step solution

Given z=32+i2=cos⁡π6+isin⁡π6z = \frac{\sqrt{3}}{2} + \frac{i}{2} = \cos\frac{\pi}{6} + i\sin\frac{\pi}{6}. By De Moivre's theorem, z201=cos⁡201π6+isin⁡201π6=cos⁡67π2+isin⁡67π2z^{201} = \cos\frac{201\pi}{6} + i\sin\frac{201\pi}{6} = \cos\frac{67\pi}{2} + i\sin\frac{67\pi}{2}. Since 67π2=33π+π2\frac{67\pi}{2} = 33\pi + \frac{\pi}{2}, we have cos⁡(33π+π2)=0\cos\left(33\pi + \frac{\pi}{2}\right) = 0 and sin⁡(33π+π2)=−1\sin\left(33\pi + \frac{\pi}{2}\right) = -1. Thus z201=−iz^{201} = -i. Then z201−i=−i−i=−2iz^{201} - i = -i - i = -2i. Hence (z201−i)8=(−2i)8=(−2)8⋅i8=256⋅(i4)2=256⋅12=256(z^{201} - i)^8 = (-2i)^8 = (-2)^8 \cdot i^8 = 256 \cdot (i^4)^2 = 256 \cdot 1^2 = 256. Therefore, the answer is 256, which corresponds to option D.

Answer key and solution verified before publishing.

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Exam
JEE Main 2026
Subject
Mathematics
Chapter
Complex Numbers
Topic
Demoivre's Theorem and Roots of Unity
If z =frac √(3) 2 +frac i 2 , i =√(-1) , then ( z 201 - i ) 8 is… | JEE Main 2026 PYQ with Solution · DhiX AI