Chapter 8: Problem 17
Sketch the set in the complex plane. $$\\{z=a+b i | a \leq 0, b \geq 0\\}$$
Short Answer
Expert verified
Shade the upper-left quadrant, including the origin and the boundaries along the negative real and positive imaginary axes.
Step by step solution
01
Understand the Set's Components
The set \( \{ z = a + bi | a \leq 0, b \geq 0 \} \) describes all complex numbers where the real part \( a \) is less than or equal to zero, and the imaginary part \( b \) is greater than or equal to zero.
02
Identify the Complex Plane Quadrants
In the complex plane, the horizontal axis represents the real part \( a \), and the vertical axis represents the imaginary part \( b \). Quadrant II is where \( a \leq 0 \) and \( b \geq 0 \).
03
Recognize the Boundaries
The condition \( a \leq 0 \) defines the left half of the plane, starting from the imaginary axis to the left. The condition \( b \geq 0 \) includes the upper half of the plane, starting from the real axis upward.
04
Combine the Conditions
The set \( \{ z = a + bi | a \leq 0, b \geq 0 \} \) includes all points that satisfy both conditions simultaneously, forming the upper-left (second) quadrant and including the boundaries where \( a = 0 \) and \( b = 0 \). Thus, the entire boundary on the imaginary axis and the real axis up to the origin is included.
05
Sketch the Set
On the complex plane, shade the upper-left quadrant (Quadrant II). This includes the entire region to the left of and above the origin, as well as the boundary lines along the negative real axis (\( b = 0 \)) and positive imaginary axis (\( a = 0 \)). Make sure to include the origin as well.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Complex Numbers
Complex numbers are numbers that consist of two parts: a real part and an imaginary part. These numbers have the general form of \( z = a + bi \), where \( a \) is the real part, and \( bi \) is the imaginary part, with \( i \) being the imaginary unit. The imaginary unit \( i \) is defined as \( \sqrt{-1} \), which means \( i^2 = -1 \). Complex numbers are used extensively in mathematics and engineering to solve equations that do not have real solutions.
Here are some important points about complex numbers:
Here are some important points about complex numbers:
- If \( b = 0 \), the number is purely real, reducing to \( a \).
- If \( a = 0 \), the number is purely imaginary, expressed as \( bi \).
- Complex numbers are crucial for performing transformations and mathematical operations that are not possible with real numbers alone.
Complex Plane Quadrants
The complex plane is a two-dimensional plane similar to the Cartesian coordinate system but designed to represent complex numbers. In this plane:
The complex plane is divided into four quadrants, each with distinct conditions for \( a \) and \( b \):
- The horizontal axis is the real axis, representing the real component \( a \).
- The vertical axis is the imaginary axis, representing the imaginary component \( b \).
The complex plane is divided into four quadrants, each with distinct conditions for \( a \) and \( b \):
- Quadrant I: both \( a \) and \( b \) are positive.
- Quadrant II: \( a \leq 0 \) and \( b \geq 0 \), meaning here \( a \) is non-positive and \( b \) is non-negative.
- Quadrant III: both \( a \) and \( b \) are negative.
- Quadrant IV: \( a \geq 0 \) and \( b \leq 0 \), with \( a \) non-negative and \( b \) non-positive.
Graphing in the Complex Plane
Graphing complex numbers in the complex plane involves plotting their points based on the values of \( a \) and \( b \). Each complex number \( z = a + bi \) corresponds to a unique point \( (a, b) \) in the plane. To graph the given set \( \{ z = a + bi | a \leq 0, b \geq 0 \} \):
- Identify the conditions: Here, \( a \leq 0 \) and \( b \geq 0 \) means you are looking to fill the upper-left quarter of the plane, which is Quadrant II.
- Consider the boundaries: Set includes the entire negative side and upper side of the plane up to the origin, embracing the sections where \( a = 0 \) (imaginary axis) and \( b = 0 \) (real axis).
- Shade the region: Shade the entire Quadrant II along with the boundaries to indicate inclusion of all points \( (a, b) \) meeting the criteria.