Chapter 1: Problem 13
Show that the equation of the line through the points \(z_{1}\) and \(z_{2}\) can be expressed in the form \(z=z_{1}+t\left(z_{2}-z_{1}\right)\), where \(t\) is a real number.
Short Answer
Expert verified
The line through points \(z_1\) and \(z_2\) is expressed as \(z = z_1 + t(z_2 - z_1)\), where \(t\) is real.
Step by step solution
01
Understand the Concept of a Line in the Complex Plane
First, we need to understand that a line in the complex plane through two points can be thought of similarly to a line in the Cartesian coordinate plane. If you have two points \(z_1 = x_1 + iy_1\) and \(z_2 = x_2 + iy_2\), the line can be expressed as the set of points \(z\) where \(z = z_1 + t(z_2 - z_1)\), with \(t\) being a real number.
02
Express the Points as Complex Numbers
Consider the points \(z_1 = x_1 + iy_1\) and \(z_2 = x_2 + iy_2\) which are complex numbers. The difference between these two points is \(z_2 - z_1 = (x_2 - x_1) + i(y_2 - y_1)\), which gives us the direction of the line in the complex plane.
03
Parametric Equation of the Line
The parametric equation for a line extending from \(z_1\) towards \(z_2\) can be written as \(z = z_1 + t(z_2 - z_1)\), where \(t\) is any real number. Here, \(t\) scales the difference \(z_2 - z_1\), moving the point \(z\) along the direction of the line.
04
Substitute Difference into Parametric Equation
Substitute \(z_2 - z_1 = (x_2 - x_1) + i(y_2 - y_1)\) into the equation. This results in \(z = z_1 + t((x_2 - x_1) + i(y_2 - y_1))\), demonstrating that \(z\) is indeed any point on the line through \(z_1\) and \(z_2\).
05
Verify the Line Behaves as Expected
When \(t = 0\), \(z = z_1\), and when \(t = 1\), \(z = z_2\). Thus, the equation correctly expresses the line passing through both \(z_1\) and \(z_2\). This verifies our parametric representation as accurate.
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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 where complex numbers are represented as points. This is also known as the Argand plane. Complex numbers are of the form \( z = x + iy \), where \( x \) is the real part and \( y \) is the imaginary part. The complex plane helps visualize complex numbers and their operations, much like the Cartesian coordinate system does for real numbers.
- Real axis: This is the horizontal axis representing the real part of the complex number.
- Imaginary axis: This is the vertical axis representing the imaginary part of the complex number.
Parametric Equations
Parametric equations are a way of defining a set of points using one or more parameters, typically describing a path or a curve in a space. When it comes to lines in the complex plane, a parametric equation describes the line using a parameter, usually denoted by \( t \). In the context of complex numbers, consider two points \( z_1 \) and \( z_2 \) in the complex plane. The line passing through these points can be expressed with the parametric equation:\[ z = z_1 + t(z_2 - z_1) \]
- \( z_1 + t(z_2 - z_1) \): \( z \) represents a point on the line. \( z_1 \) is a starting point, while \( z_2 - z_1 \) gives the direction of the line.
- \( t \): This real parameter 'stretches' or 'shrinks' the segment \( z_2 - z_1 \). By changing \( t \), we can locate any point along the line.
Complex Numbers
Complex numbers are numbers that have both a real part and an imaginary part, typically written as \( z = x + iy \), where \( x \) is the real part and \( iy \) is the imaginary part. Each complex number corresponds to a point in the complex plane. Key properties and operations with complex numbers include:
- Conjugate: The complex conjugate of \( z = x + iy \) is \( \overline{z} = x - iy \). It reflects the point across the real axis.
- Magnitude: The magnitude (or modulus) of \( z \) is \( |z| = \sqrt{x^2 + y^2} \). This is the distance of the point from the origin.
- Addition/Subtraction: Two complex numbers are added by summing their real parts and imaginary parts separately.
- Multiplication: Multiply by expanding \( (x + iy)(a + ib) = (xa - yb) + i(xb + ya) \).