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Use de Moivre's Theorem to find the following. Write your answer in standard form.[2(cos 20° + i sin 20°)]3

Question

Use de Moivre's Theorem to find the following. Write your answer in standard form.

2(cos20+isin20)3 2(\cos 20^{\circ} + i \sin 20^{\circ})^{3}

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Solution

De Moivre's Theorem states that for any real number x and integer n, [cos(x) + i sin(x)]^n = cos(nx) + i sin(nx).

We can apply this theorem to the given problem as follows:

Given: [2(cos 20° + i sin 20°)]^3

Step 1: Apply De Moivre's Theorem = 2^3 [cos(320°) + i sin(320°)] = 8 [cos(60°) + i sin(60°)]

Step 2: Evaluate the trigonometric functions = 8 [1/2 + i * sqrt(3)/2] = 4 + 4i sqrt(3)

So, [2(cos 20° + i sin 20°)]^3 = 4 + 4i sqrt(3) in standard form.

This problem has been solved

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