Comprehension

Let z =  where i = 

What is angle θ such that z is purely imaginary ?

where n is an integer

This question was previously asked in
NDA 02/2022 Mathematics Official Paper (Held On 04 Sep 2022)
View all NDA Papers >
  1. 2nπ

Answer (Detailed Solution Below)

Option 2 :
Free
NDA 01/2025: English Subject Test
30 Qs. 120 Marks 30 Mins

Detailed Solution

Download Solution PDF

Concept:

If z = x + iy is purely imaginary, then x = 0

Calculation:

Given, 

z =  where i = 

Multiply numerator and denominator by (1 + i sin θ), 

,

Since z is purely imaginary,

⇒ 

⇒ cos2θ = 0

⇒ θ =  

∴ The correct answer is option (2).

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