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IrinaK [193]
3 years ago
6

Find the complex fourth roots of 81(cos(3pi/8) + i sin(3pi/8))

Mathematics
1 answer:
BartSMP [9]3 years ago
7 0
By using <span>De Moivre's theorem:
</span>
If we have the complex number ⇒ z = a ( cos θ + i sin θ)
∴ \sqrt[n]{z} =  \sqrt[n]{a} \ (cos \  \frac{\theta + 360K}{n} + i \ sin \ \frac{\theta +360k}{n} )
k= 0, 1 , 2, ..... , (n-1)


For The given complex number <span>⇒ z = 81(cos(3π/8) + i sin(3π/8))
</span>

Part (A) <span>find the modulus for all of the fourth roots
</span>
<span>∴ The modulus of the given complex number = l z l = 81
</span>
∴ The modulus of the fourth root = \sqrt[4]{z} =  \sqrt[4]{81} = 3

Part (b) find the angle for each of the four roots

The angle of the given complex number = \frac{3 \pi}{8}
There is four roots and the angle between each root = \frac{2 \pi}{4} =  \frac{\pi}{2}
The angle of the first root = \frac{ \frac{3 \pi}{8} }{4} =  \frac{3 \pi}{32}
The angle of the second root = \frac{3\pi}{32} +  \frac{\pi}{2} =  \frac{19\pi}{32}
The angle of the third root = \frac{19\pi}{32} +  \frac{\pi}{2} =  \frac{35\pi}{32}
The angle of the  fourth root = \frac{35\pi}{32} +  \frac{\pi}{2} =  \frac{51\pi}{32}

Part (C): find all of the fourth roots of this

The first root = z_{1} = 3 ( cos \  \frac{3\pi}{32} + i \ sin \ \frac{3\pi}{32})
The second root = z_{2} = 3 ( cos \  \frac{19\pi}{32} + i \ sin \ \frac{19\pi}{32})

The third root = z_{3} = 3 ( cos \  \frac{35\pi}{32} + i \ sin \ \frac{35\pi}{32})
The fourth root = z_{4} = 3 ( cos \  \frac{51\pi}{32} + i \ sin \ \frac{51\pi}{32})
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Answer:

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Car Wash A theater group is having a carwash fundraiser. The liquid soap costs $31 and is enough to wash 40 cars. Each car is ch
zheka24 [161]

Answer:

A) Independent variable is "c"

Dependent variable is "p"

B) Yes, it's a function

C) p = 7c - 31

D)domain of the function: 0 ≤ c ≤ 40

Range of the function: 0 ≤ p ≤ 249

Step-by-step explanation:

A) c is the total number of cars washed and p is the profit. The profit depends on the total number of cars washed. Hence, profit(p) is the dependent variable while "c" is independent variable

B) Yes it's a function because for each number of cars washed, there is a distinct value of profit made.

C) We are told that the liquid soap costs $31 and is enough to wash 40 cars. Each car is charged 7$.

$31 is cost to wash one car. Thus profit made per car is;

p = 7c - 31

D) The cost of $31 liquid soap is enough to only wash a maximum of 40 cars. This means the domain for the cars is from 0 cars to 40 cars

Thus;

domain of the function is 0 ≤ c ≤ 40

The profit function is given in answer C above as p = 7c - 31.

Now, if 0 cars are washed they will make zero profit but if 40 cars are washed then;

p = 7(40) - 31

p = 280 - 31

p = 249

Range of the function: 0 ≤ p ≤ 249

8 0
3 years ago
A ball is kicked upward with an initial velocity of 32 feet per second. The ball's height, h (in feet), from the ground is model
stellarik [79]

Answer:

1.        t = 0.995 s

2.       h = 15.92  ft

Step-by-step explanation:

First we have to look at the following formula

Vf = Vo + gt

then we work it to clear what we want

Vo + gt = Vf

gt = Vf - Vo

t = (Vf-Vo)/g

Now we have to complete the formula with the real data

Vo = 32 ft/s      as the statement says

Vf = 0     because when it reaches its maximum point it will stop before starting to lower

g = -32,16 ft/s²        it is a known constant, that we use it with the negative sign because it is in the opposite direction to ours

t = (0 ft/s - 32 ft/s) / -32,16 ft/s²

we solve and ...

t = 0.995 s

Now we will implement this result in the following formula to get the height at that time

h = (Vo - Vf) *t /2

h = (32 ft/s - 0 ft/s) * 0.995 s / 2

h = 32 ft/s * 0.995 s/2

h = 31.84 ft / 2

h = 15.92  ft

4 0
3 years ago
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