Chapter 10: Problem 65
Graph the lines and conic sections. $$r=3 \sec (\theta-\pi / 3)$$
Short Answer
Expert verified
The line is vertical at \(x=3\) in Cartesian coordinates.
Step by step solution
01
Convert Polar to Cartesian Form
The given polar equation is \[ r = 3 \sec \left( \theta - \frac{\pi}{3} \right) \] First, recall that \( \sec(\theta) = \frac{1}{\cos(\theta)} \). This implies \[ r = \frac{3}{\cos \left( \theta - \frac{\pi}{3} \right) } \]. This corresponds to a line because secant functions in polar coordinates indicate vertical lines. To convert this to a Cartesian equation, use the identities: \( x = r \cos(\theta) \) and \( y = r \sin(\theta) \). We also have the identity \[ x = 3. \] This is the horizontal line at \(x=3\).
02
Plot the Cartesian Equation
Now that we have the Cartesian version of the equation, which is simply \(x=3\), plot this equation on a coordinate grid.This represents a vertical line passing through the x-axis at \(x = 3\). The line extends vertically in both directions across the y-axis. It is important to note that all points on the line have an x-coordinate of 3, signifying that the line does not vary in the x direction.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Lines
Graphing lines is a fundamental aspect of understanding coordinate systems. Lines in Cartesian coordinates are represented as linear equations like \(y = mx + b\), where \(m\) is the slope and \(b\) is the y-intercept. A vertical line, like the one we discussed with \(x = 3\), is unique because it doesn't vary in the x-direction; its equation features invariable x-values. This means wherever you find yourself on the line, the x-coordinate remains consistent.
When graphing a line such as \(x = 3\), include:
When graphing a line such as \(x = 3\), include:
- Plotting points along the x-coordinate 3
- Drawing a straight vertical line extending through points at x = 3 on both positive and negative y-directions
Conic Sections
Conic sections are the curves obtained by slicing a right circular cone with a plane. There are four main types: circles, ellipses, parabolas, and hyperbolas. Each has distinct properties and equations:
- Circles: All points are at a constant distance from the center. The equation is \((x-h)^2 + (y-k)^2 = r^2\).
- Ellipses: Similar to circles but stretched along one axis. An ellipse's equation is \(\frac{(x-h)^2}{a^2} + \frac{(y-k)^2}{b^2} = 1\).
- Parabolas: Curves where any point is the same distance from a fixed point (focus) and a line (directrix). The equation is usually \(y = ax^2 + bx + c\).
- Hyperbolas: Two similar open curves that are mirror images. The typical equation is \(\frac{(x-h)^2}{a^2} - \frac{(y-k)^2}{b^2} = 1\).
Polar Coordinates
Polar coordinates represent points in a plane using a radius and angle, denoted as \( (r, \theta) \). This system is particularly effective in scenarios involving circular and radial patterns, as it reflects angles and distances from a central point.
To convert between polar and Cartesian coordinates, employ the following relationships:
To convert between polar and Cartesian coordinates, employ the following relationships:
- Circular Systems: Defined by the center and angle. Begin with the polar coordinates \(r = 3 \sec(\theta - \frac{\pi}{3})\), which implies a line in polar form.
- Conversion to Cartesian: Utilize \(x = r \cos(\theta)\) and \(y = r \sin(\theta)\) to translate polar equations into Cartesian. Thus, polar lines transition into vertical or horizontal lines in Cartesian coordinates.