Which expression is a rational number? A) ( 25 + 25 )2 B) ( 25 + 50 )2 C) ( 50 + 75 )2 D) ( 25 + 72 )2
1 answer:
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Answer:
see explanation
Step-by-step explanation:
Using De Moivre's theorem
Given
[ 4(cos15° + isin15° ) ]³, then
= 4³ [ cos(3 × 15°) + isin(3 × 15°) ]
= 64 (cos45° + isin45° )
= 64 ( +
i )
= 64 ( (1 + i) )
= 32 (1 + i)
= 32 + 32
i