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Find the following power. Write the answer in rectangular form.

[tex]\[
\left( \sqrt{2} - \sqrt{2} i \right)^8
\][/tex]

Simplify your answer, including any radicals. Use integers or fractions in the expression. Type your answer in the form [tex]\( a + b i \)[/tex].

Sagot :

To find [tex]\((\sqrt{2} - \sqrt{2}i)^8\)[/tex] and write the answer in rectangular form, we can follow these steps:

1. Express the complex number in polar form:
[tex]\[ z = \sqrt{2} - \sqrt{2}i \][/tex]
We write [tex]\(z\)[/tex] in the polar form [tex]\(re^{i\theta}\)[/tex] where [tex]\(r\)[/tex] is the modulus and [tex]\(\theta\)[/tex] is the argument (angle).

2. Calculate the modulus [tex]\(r\)[/tex]:
[tex]\[ r = \sqrt{(\sqrt{2})^2 + (-\sqrt{2})^2} = \sqrt{2 + 2} = \sqrt{4} = 2 \][/tex]

3. Find the argument [tex]\(\theta\)[/tex]:
The argument [tex]\(\theta\)[/tex] can be found using the arctangent function:
[tex]\[ \theta = \arctan\left(\frac{-\sqrt{2}}{\sqrt{2}}\right) = \arctan(-1) = -\frac{\pi}{4} \][/tex]
Therefore, in polar form:
[tex]\[ z = 2e^{-i\pi/4} \][/tex]

4. Use De Moivre's Theorem to raise [tex]\(z\)[/tex] to the 8th power:
According to De Moivre's Theorem:
[tex]\[ z^n = (re^{i\theta})^n = r^n e^{in\theta} \][/tex]
Applying this to our problem:
[tex]\[ z^8 = \left(2e^{-i\pi/4}\right)^8 = 2^8 e^{-i 8 \cdot \pi/4} \][/tex]
Simplify the exponent:
[tex]\[ e^{-i 8 \pi/4} = e^{-i 2 \pi} = e^{0} = 1 \][/tex]
Thus,
[tex]\[ z^8 = 2^8 \cdot 1 = 2^8 = 256 \][/tex]

5. Convert back to rectangular form:
The result can be written as:
[tex]\[ 256 + 0i \][/tex]

Therefore, the result of [tex]\((\sqrt{2} - \sqrt{2}i)^8\)[/tex] in rectangular form is:
[tex]\[ \boxed{256 + 0i} \][/tex]
Or simplified:
[tex]\[ \boxed{256} \][/tex]