Question

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$2 \sqrt{2} ( \cos \frac{\pi}{4} + i \sin \frac{\pi}{4} )$
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Answer 1

Answer:

SO ACCORDING TO ME THE ANSWER SHOULD BE (4)

Hope it will help you..

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Answer 2

Answer:

We know that 

cos(A+B)=cosAcosB−sinAsinB

cos(4π+A)=cos4πcosA−sin4πsinA

cos(4π+A)=21cosA−21sinA

2cos(4π+A)=cosA−sinA

Hence Proved