Chapter 10: Problem 16
Plot each complex number in the complex plane and write it in polar form and in exponential form. $$ 1-\sqrt{3} i $$
Short Answer
Expert verified
Polar: 2(\cos(-\frac{\pi}{3}) + i\sin(-\frac{\pi}{3})), Exponential: 2 e^{-i \frac{\pi}{3}}.
Step by step solution
01
- Determine the real and imaginary parts
Let’s identify the real and imaginary parts of the complex number. Given the complex number is \(1 - \sqrt{3}i\). Here, the real part (a) is 1 and the imaginary part (b) is -\(\sqrt{3}\).
02
- Plot the number in the Complex Plane
Plot the point (1, -√3) on the complex plane. This corresponds to moving 1 unit to the right on the real axis and \(-\sqrt{3}\) units downward on the imaginary axis.
03
- Calculate the modulus (r)
The modulus of the complex number is calculated as: \[ r = \sqrt{a^2 + b^2} \] Substituting the values, we get: \[ r = \sqrt{1^2 + (-\sqrt{3})^2} = \sqrt{1 + 3} = \sqrt{4} = 2 \]
04
- Calculate the argument (θ)
The argument is calculated using the arctangent function: \[ \theta = \tan^{-1}\left(\frac{b}{a}\right) \] Substituting the values, we get: \[ \theta = \tan^{-1}\left(\frac{-\sqrt{3}}{1}\right) = \tan^{-1}(-\sqrt{3}) \]. Since the number is in the fourth quadrant, θ = \(-\frac{\pi}{3}\).
05
- Write the polar form
The polar form of a complex number is given by: \[ z = r (\cos \theta + i \sin \theta) \] Substituting the values, we get: \[ z = 2 (\cos(-\frac{\pi}{3}) + i \sin(-\frac{\pi}{3})) \]
06
- Write the exponential form
The exponential form of a complex number is given by: \[ z = r e^{i\theta} \] Substituting the values, we get: \[ z = 2 e^{-i\frac{\pi}{3}} \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Complex Plane
The complex plane is a two-dimensional plane. Here, a complex number is represented graphically. The horizontal axis represents the real part of the number while the vertical axis represents the imaginary part. For example, the number \(1 - \sqrt{3}i\) can be plotted by moving 1 unit to the right (along the real axis) and \(-\sqrt{3}\) units downwards (along the imaginary axis).
- Real Axis: Horizontal axis
- Imaginary Axis: Vertical axis
- Coordinate: (Real, Imaginary)
Polar Form
Polar form expresses a complex number in terms of modulus and argument. This form is very useful in understanding the magnitude and direction of a complex number.
- Modulus (r): Distance from origin
- Argument (θ): Angle with the positive real axis
Exponential Form
The exponential form of a complex number is another way to represent it, using Euler's formula. It ties together the polar form with an exponent involving the imaginary unit, i.
- Formula: \(z = re^{i\theta}\)
- Relationship: Links the magnitude and phase angle
Modulus
The modulus of a complex number is its distance from the origin on the complex plane. It's calculated using the Pythagorean theorem: \[ r = \sqrt{a^2 + b^2} \].
- For \(a = 1\) and \(b = -\sqrt{3}\): \( r = 2 \)
- Interpretation: Magnitude of the number
Argument
The argument of a complex number is the angle it makes with the positive real axis. It's calculated using the arctangent function: \[ \theta = \tan^{-1}(\frac{b}{a}) \].
- Placement: Fourth quadrant
- Value: \(\theta = -\frac{\pi}{3}\)