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Tresset [83]
3 years ago
11

Use​ DeMoivre's Theorem to find the indicated power of the complex number. Write the answer in rectangular form.

Mathematics
1 answer:
slava [35]3 years ago
3 0

Answer:

After solving the power:

\bold{2(cos60^\circ+isin60^\circ)}

Rectangular form:

\bold{1+i\sqrt3}

Step-by-step explanation:

Given the complex number:

2(cos20^\circ+isin20^\circ)^3

To find:

The indicated power by using De Moivre's theorem.

The complex number in rectangular form.

Rectangular form of a complex number is given as a+ib where a and b are real numbers.

Solution:

First of all, let us have a look at the De Moivre's theorem:

(cos\theta+isin\theta )^n=cos(n\theta)+isin(n\theta )

First of all, let us solve:

(cos20^\circ+isin20^\circ)^3

Let us apply the De Moivre's Theorem:

Here, n = 3

(cos20^\circ+isin20^\circ)^3 = cos(3 \times 20)^\circ+isin(3 \times 20)^\circ\\\Rightarrow cos60^\circ+isin60^\circ

Now, the given complex number becomes:

2(cos60^\circ+isin60^\circ)

Let us put the values of cos60^\circ = \frac{1}{2} and sin60^\circ = \frac{\sqrt3}{2}

2(\dfrac{1}{2}+i\dfrac{\sqrt3}2)\\\Rightarrow (2 \times \dfrac{1}{2}+i\dfrac{\sqrt3}2\times 2)\\\Rightarrow \bold{1 +i\sqrt3 }

So, the rectangular form of the given complex number is:

\bold{1+i\sqrt3}

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One supplementary angle is 15 degrees less than twice the other. Find the measure of the two supplementary angles.
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Hey there!

To find our answer, we need to set up a <u><em>system of equations. </em></u>Remember, <u><em>supplementary angles</em></u> equal 180 degrees when combined. We will call one of our angles A and the other one B. Let's set it up below! :)

A=2B-15 (one angle is 15 degrees less than twice the other)

A+B=180

We need to find one of our variables. To do this, we only put one variable in the equation. But how, there are two variables in both equations! Well, as you can see, we see the A is equal to 2B-15, so we can take 2B-15 and put it into the second equation in place of A because it is equal to A, and then we will only have Bs and we can solve for it. This method is known as solving systems of equations with <u><em>substitution.</em></u>

Let's solve with substitution!

2B-15+B=180

3B-15=180              We combine our Bs.

3B=195              We add 15 to both sides.

B= 65                We divide both sides by three.

Now, we need to find what A is, but this will be really easy to do! If you remember, our angles are supplementary, so when you combine them, we will get 180, as you can see in our second equation in our first system of equations. So, we simply subtract 65 from 180.

180-65=115

Our two angles are 65° and 115°.

We can also check this with the original problem.

If you double 65, we have 130. Then, if we subtract 15, we have 115. Systems of equations are a pretty awesome way to figure this out!

I hope this helps! Have a great day!

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The balloon reaches a height of 7 feet at 0.1 seconds and 2.13 seconds

<h3>How to determine the time the balloon is at the height?</h3>

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