document.write( "Question 283747: calculate (cos θ + i*sin θ)^4 in two different ways, and obtain identities for cos 4θ and sin 4θ. \n" ); document.write( "

Algebra.Com's Answer #206067 by jim_thompson5910(35256) $\"\"$ $\"About$

You can put this solution on YOUR website!
Hint: the first way is to expand the by either binomial expansion or just remembering that

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\n" ); document.write( "\n" ); document.write( "The second way is to use De Moivre's theorem which states that $\"%28cos%28x%29%2Bi%2Asin%28x%29%29%5En=cos%28nx%29%2Bi%2Asin%28nx%29\"$ for any complex number 'x' and integer 'n'. \n" ); document.write( "

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