Math Problem Statement

Solve number 1 a

Solve number 1(a): \[ \frac{(1 + i)^{28}}{(1 - i)^{24} - i(1 + i)^{24}} \] where \( i \) is the imaginary unit such that \( i^2 = -1 \).

Solution

To solve problem 1(a), which is an algebraic expression in complex numbers, we need to evaluate:

(1+i)28(1i)24i(1+i)24\frac{(1 + i)^{28}}{(1 - i)^{24} - i(1 + i)^{24}}

where ii is the imaginary unit such that i2=1i^2 = -1.

Let's break down the expression step by step.

Step 1: Simplify (1+i)(1 + i) and (1i)(1 - i)

  1. Magnitude of 1+i1 + i: 1+i=12+12=2|1 + i| = \sqrt{1^2 + 1^2} = \sqrt{2} So, we can write 1+i1 + i in polar form as: 1+i=2(cosπ4+isinπ4)1 + i = \sqrt{2} \left(\cos \frac{\pi}{4} + i \sin \frac{\pi}{4}\right)

  2. Magnitude of 1i1 - i: 1i=12+(1)2=2|1 - i| = \sqrt{1^2 + (-1)^2} = \sqrt{2} And similarly: 1i=2(cos(π4)+isin(π4))1 - i = \sqrt{2} \left(\cos \left(-\frac{\pi}{4}\right) + i \sin \left(-\frac{\pi}{4}\right)\right)

Step 2: Use De Moivre's Theorem

Using De Moivre’s Theorem:

  1. Compute (1+i)28(1 + i)^{28}: (1+i)28=(2)28(cos28π4+isin28π4)(1 + i)^{28} = \left(\sqrt{2}\right)^{28} \left(\cos \frac{28\pi}{4} + i \sin \frac{28\pi}{4}\right) Since 28π4=7π\frac{28\pi}{4} = 7\pi, which is equivalent to π\pi (since 7π7\pi is an odd multiple of π\pi), (1+i)28=214(cosπ+isinπ)=214(1)=214(1 + i)^{28} = 2^{14} (\cos \pi + i \sin \pi) = 2^{14} (-1) = -2^{14}

  2. Compute (1i)24(1 - i)^{24}: (1i)24=(2)24(cos24π4+isin24π4)(1 - i)^{24} = \left(\sqrt{2}\right)^{24} \left(\cos \frac{-24\pi}{4} + i \sin \frac{-24\pi}{4}\right) Since 24π4=6π\frac{-24\pi}{4} = -6\pi, which is equivalent to 00 (since 6π-6\pi is an even multiple of π\pi), (1i)24=212(cos0+isin0)=212(1 - i)^{24} = 2^{12} (\cos 0 + i \sin 0) = 2^{12}

Step 3: Substitute and Simplify

Now, substitute back into the expression: (1+i)28(1i)24i(1+i)24\frac{(1 + i)^{28}}{(1 - i)^{24} - i(1 + i)^{24}}

Since (1+i)24=212(cosπ+isinπ)=212(1 + i)^{24} = 2^{12} (\cos \pi + i \sin \pi) = -2^{12}, we can substitute

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Algebra
Exponents
Polar Form of Complex Numbers

Formulas

De Moivre's Theorem: (r (cos θ + i sin θ))^n = r^n (cos nθ + i sin nθ)
Polar Form of Complex Numbers: a + bi = r (cos θ + i sin θ), where r = √(a^2 + b^2) and θ = arctan(b/a)

Theorems

De Moivre's Theorem

Suitable Grade Level

Grades 11-12 or Undergraduate Level