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Consider the complex number 
z=-2sqrt3+2i.
What is 
z^(3) ?
Hint: 
z has a modulus of 4 and an argument of 
150^(@).
Choose 1 answer:
(A) 
-6-10.4 i
(B) 
64 i
(c) 
-10.4+6i
(D) 
-32-55.4 i

Consider the complex number z=23+2i z=-2 \sqrt{3}+2 i .\newlineWhat is z3 z^{3} ?\newlineHint: z z has a modulus of 44 and an argument of 150 150^{\circ} .\newlineChoose 11 answer:\newline(A) 610.4i -6-10.4 i \newline(B) 64i 64 i \newline(C) 10.4+6i -10.4+6 i \newline(D) 3255.4i -32-55.4 i

Full solution

Q. Consider the complex number z=23+2i z=-2 \sqrt{3}+2 i .\newlineWhat is z3 z^{3} ?\newlineHint: z z has a modulus of 44 and an argument of 150 150^{\circ} .\newlineChoose 11 answer:\newline(A) 610.4i -6-10.4 i \newline(B) 64i 64 i \newline(C) 10.4+6i -10.4+6 i \newline(D) 3255.4i -32-55.4 i
  1. Given complex number: We are given the complex number z=23+2iz = -2\sqrt{3} + 2i. We are also given that zz has a modulus of 44 and an argument of 150150 degrees. To find z3z^3, we can use De Moivre's Theorem, which states that (r(cos(θ)+isin(θ)))n=rn(cos(nθ)+isin(nθ))(r(\cos(\theta) + i \sin(\theta)))^n = r^n (\cos(n\theta) + i \sin(n\theta)), where rr is the modulus and θ\theta is the argument of the complex number.
  2. Convert to radians: First, we convert the argument of 150150 degrees to radians because trigonometric functions in the complex plane are typically expressed in radians. 150150 degrees is equivalent to 150×(π/180)=5π6150 \times (\pi/180) = \frac{5\pi}{6} radians.
  3. Apply De Moivre's Theorem: Now we can apply De Moivre's Theorem. We have r=4r = 4 and θ=5π6\theta = \frac{5\pi}{6}. We want to find z3z^3, so we raise the modulus to the power of 33 and multiply the argument by 33.r3=43=64r^3 = 4^3 = 64θ×3=5π6×3=5π2\theta \times 3 = \frac{5\pi}{6} \times 3 = \frac{5\pi}{2}
  4. Simplify argument: Using De Moivre's Theorem, we get: \newlinez3=64×(cos(5π2)+isin(5π2))z^3 = 64 \times (\cos(\frac{5\pi}{2}) + i \sin(\frac{5\pi}{2}))\newlineSince the sine and cosine functions are periodic with a period of 2π2\pi, we can simplify the argument 5π2\frac{5\pi}{2} to π2\frac{\pi}{2} by subtracting 2π2\pi (which is one full period) from 5π2\frac{5\pi}{2}.\newline5π22π=π2\frac{5\pi}{2} - 2\pi = \frac{\pi}{2}
  5. Find cosine and sine: Now we can find the cosine and sine of π/2\pi/2: \newlinecos(π/2)=0\cos(\pi/2) = 0\newlinesin(π/2)=1\sin(\pi/2) = 1\newlineSo, z3=64×(0+i×1)=64iz^3 = 64 \times (0 + i \times 1) = 64i

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