The value of is equal to

(A) 4

(B) 6

(C) 8

(D) 2

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Answer:(D)

Explanation:

We have

[by De-Moivre’s theorem]

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The solution of the equation is

(A)

(B)

(C)

(D)

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Answer:(A)

Explanation:

Let

Comparing real and imaginary parts

we have and

Now substitute the value of in we get

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If is purely imaginary, then

(A)

(B)

(C)

(D) None of these

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Answer:(C)

Explanation:

Let , where

As we know by componendo and dividendo that

So we have

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