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Convert each polar equation to a rectangular equation. \(r=\frac{8}{2-\sin \theta}\)

Short Answer

Expert verified
\(2 \sqrt{x^2 + y^2} = y + 8\)

Step by step solution

01

Use the relationship between polar and rectangular coordinates

Recall the relationship between polar and rectangular coordinates: \(x = r \, \text{cos} \, \theta\) \(y = r \, \text{sin} \, \theta\) \(r^2 = x^2 + y^2\)
02

Substitute known values

The given polar equation is \(r = \frac{8}{2 - \text{sin} \, \theta}\). Multiply both sides by \(2 - \text{sin} \, \theta\) to clear the fraction: \(r(2 - \text{sin} \, \theta) = 8\)
03

Express sin(θ) in terms of rectangular coordinates

Using the relationship \(y = r \, \text{sin} \, \theta\), we get \(\text{sin} \, \theta = \frac{y}{r}\). Substitute this into the equation from Step 2: \(r \left(2 - \frac{y}{r}\right) = 8\)
04

Simplify the equation

Distribute \(r\) on the left-hand side: \(2r - y = 8\)
05

Solve for r

Recall from Step 1 that \(r = \sqrt{x^2 + y^2}\). Substitute \(r = \sqrt{x^2 + y^2}\) into the simplified equation: \(2 \sqrt{x^2 + y^2} - y = 8\)
06

Arrange into the standard form

Isolate the term with the square root to one side: \(2 \sqrt{x^2 + y^2} = y + 8\). Finally, simplify the equation into rectangular form.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

rectangular coordinates
Rectangular coordinates are a way to represent points in a plane using two distances from two perpendicular lines known as the x-axis and y-axis. Each point is defined by an ordered pair \(x, y\). The x-coordinate tells you how far to move left or right, and the y-coordinate tells you how far to move up or down. Rectangular coordinates are commonly used because they allow straightforward calculation using basic algebraic operations. You can visualize rectangular coordinates like a city grid, with streets running horizontally and avenues running vertically.
polar coordinates
Polar coordinates represent points in a plane using a distance from a fixed point (the origin) and an angle from a fixed direction (usually the positive x-axis). Each point is defined by \(r, \theta\), where \(r\) is the radial distance and \(\theta\)\ is the angle measured in radians or degrees.
Polar coordinates are particularly useful in scenarios involving circular or spiral patterns, as they simplify many mathematical descriptions and calculations. While rectangular coordinates frame a point by its horizontal and vertical distances, polar coordinates frame a point by how far it is from the origin and in what direction.
trigonometric identities
Trigonometric identities are equations that relate the trigonometric functions to one another. They are foundational to converting between polar and rectangular forms, as they allow for the expression of sines and cosines in terms of x and y coordinates.
The primary trigonometric identities used for polar to rectangular conversion are:
  • \(x = r \cos \theta\)
  • \(y = r \sin \theta\)
  • \(r = \sqrt{x^2 + y^2}\)
  • \(\theta = \tan^{-1} (y/x)\)
These identities help transform the polar equation into a form that only involves x and y, making it easier to work with in algebraic or geometric problems.
algebraic manipulation
Algebraic manipulation involves rearranging and simplifying equations using algebraic operations. After converting a polar equation to involve sines and cosines, you’ll usually need to use algebra to further simplify or rearrange the terms.
In transforming polar to rectangular equations, common algebraic manipulations include:
  • Multiplying both sides of an equation to eliminate fractions
  • Substituting trigonometric expressions with their rectangular equivalents
  • Isolating terms involving \(x\) and \(y\) on one side of the equation
For example, in the given problem, distributing \(r\) and then substituting \(r = \sqrt{x^2 + y^2}\) simplifies the equation into a rectangular form.
coordinate transformation
Coordinate transformation is the process of converting coordinates from one system to another, such as from polar to rectangular coordinates. This transformation is essential in contexts where one coordinate system may simplify the physics or geometry of a problem.
To convert from polar to rectangular coordinates, you use the established relationships between \(x, y, r,\) and \(\theta\). In our example, the steps follow a logical order:
  • Express the given polar equation as a function of \(r\) and \(\theta\)
  • Replace sines and cosines with their rectangular form equivalents
  • Resolve the resulting equation to express \(r\) using \(x, y\)
  • Finally, solve any remaining algebraic expressions to purely involve x and y
Such transformations allow solving complex problems by leveraging the strengths of different coordinate systems.

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