Chapter 11: Problem 23
Graph the sets of points whose polar coordinates satisfy the equations and inequalities. $$\pi / 4 \leq \theta \leq 3 \pi / 4, \quad 0 \leq r \leq 1$$
Short Answer
Expert verified
A sector between angles \(\theta = \pi/4\) and \(\theta = 3\pi/4\), with radius up to 1.
Step by step solution
01
Identify Angle Range
The given angle range is \(\pi / 4 \leq \theta \leq 3\pi / 4\). This means we are considering an angular sector that starts at angle \(\pi/4\) and ends at angle \(3\pi/4\). Both these angles correspond to lines radiating from the origin in the polar coordinate system.
02
Identify Radius Range
The radius range is \(0 \leq r \leq 1\). This indicates a range of points that lies between the origin and a circle of radius 1.
03
Visualize the Sector
In a polar coordinate system, the sector formed by the angles \(\pi/4\) and \(3\pi/4\) with radius from 0 to 1 creates a circular wedge. This wedge starts at the ray \(\theta = \pi/4\), ends at the ray \(\theta = 3\pi/4\), and reaches out to \(r = 1\).
04
Plot the Lines
First, draw the line corresponding to \(\theta = \pi/4\) by finding points with this angle and varying radius up to 1. Do the same for \(\theta = 3\pi/4\). These lines define the boundaries of your sector.
05
Plot the Enclosed Circle Arc
Since \(r\) varies from 0 to 1, plot an arc of a circle with radius 1 between the lines \(\theta = \pi/4\) and \(\theta = 3\pi/4\) to define the outer boundary of this sector.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Angle Range in Polar Coordinates
Polar coordinates offer a unique way to describe a point in a plane. Instead of using traditional Cartesian coordinates, which rely on x and y axes, polar coordinates use an angle \(\theta\) and a radius r. The angle range, \(\theta\), specifies the direction from the origin to a point. In the exercise's context, the angle range is given as \(\pi / 4 \leq \theta \leq 3\pi / 4\).
- \(\theta = \pi/4\) aligns roughly with the typical Cartesian direction of 45 degrees.
- \(\theta = 3\pi/4\) aligns with 135 degrees.
Understanding the Radius Range
In polar coordinates, the radius (\(r\)) denotes the distance from the origin to a particular point in the polar plane. The provided solution mentions that the radius range is \(0 \leq r \leq 1\). This range limits the distance to between 0 and 1 units from the origin.
- At \(r = 0\), the point is at the origin, where all radial distances begin.
- As r increases, the point moves outward in the specified angular direction.
- The maximum value, \(r = 1\), marks the boundary of the circular wedge.
Illustrating the Circular Wedge
A circular wedge in the polar coordinate system refers to a portion of a circle defined by a particular angle range and radius. In the identified exercise, the angles \(\pi/4\) and \(3\pi/4\) serve as the boundaries for the wedge's edges, while the radius range of \(0 \leq r \leq 1\) determines its size.
- The wedge begins at the ray emitting from \(\theta = \pi/4\) and concludes at \(\theta = 3\pi / 4\).
- Within these angular constraints, \(r\) varies up to 1, shaping a sector of a circle.
- The circular segment's outer edge is defined by an arc with r = 1.