Math Problem Statement

第2题和第3题

Solution

Let's solve the second and third questions from the image provided.

Question 2:

Problem: Find the principal argument of the complex number e5+6ie^{5+6i}

Solution:

We start with the complex number in the form ea+bie^{a+bi}. Here, a=5a = 5 and b=6b = 6.

  1. Recall Euler's formula: ea+bi=ea(cos(b)+isin(b))e^{a+bi} = e^a (\cos(b) + i \sin(b))

So, e5+6i=e5(cos(6)+isin(6))e^{5+6i} = e^5 (\cos(6) + i \sin(6))

  1. The principal argument (θ) of a complex number ebie^{bi} is bmod2πb \mod 2\pi.

Therefore, Principal argument=6mod2π\text{Principal argument} = 6 \mod 2\pi

Since 66 is less than 2π6.28322\pi \approx 6.2832, the principal argument is:

θ=6\theta = 6

Question 3:

Problem: Find the rotation angle of the transformation w=z2w = z^2 at z=2iz = 2i

Solution:

  1. First, express z=2iz = 2i in polar form: z=2i=2(cosπ2+isinπ2)z = 2i = 2(\cos \frac{\pi}{2} + i \sin \frac{\pi}{2})

  2. The transformation w=z2w = z^2: w=(2i)2=4i2=4(1)=4w = (2i)^2 = 4i^2 = 4(-1) = -4

  3. Find the argument of ww: w=4=4(cosπ+isinπ)w = -4 = 4(\cos \pi + i \sin \pi)

So, the argument of ww is π\pi.

  1. The rotation angle for the transformation w=z2w = z^2 is twice the argument of zz: Rotation angle=2×π2=π\text{Rotation angle} = 2 \times \frac{\pi}{2} = \pi

Therefore, the rotation angle is π\pi.

If you have any further questions or need additional details, please let me know.

Here are 5 questions you might consider next:

  1. How do you find the magnitude of a complex number?
  2. What is Euler's formula and how is it used in complex analysis?
  3. How do you convert a complex number from rectangular form to polar form?
  4. What is the principal argument of a complex number and how is it determined?
  5. How do transformations affect the argument and magnitude of complex numbers?

Tip: When working with complex numbers, always try to convert them to polar form to make multiplication, division, and finding powers easier.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Euler's Formula
Polar Form

Formulas

Euler's formula: $ e^{a+bi} = e^a (\cos(b) + i \sin(b)) $

Theorems

Principal Argument Theorem

Suitable Grade Level

Advanced High School