Chapter 1: Problem 162
Convert the rectangular equation to polar form and sketch its graph. $$ y^{2}=4 x $$
Short Answer
Expert verified
The polar form is \( r\sin^2(\theta) = 4\cos(\theta) \); it sketches as a rightward-opening parabola.
Step by step solution
01
Understand the Given Equation
The given equation is a parabola, represented in rectangular coordinates as \( y^2 = 4x \). In this form, the equation describes a parabola opening to the right, with its vertex at the origin (0,0).
02
Recall Polar Coordinates
In polar coordinates, each point is described by its distance from the origin, \( r \), and the angle \( \theta \) it makes with the positive x-axis. The relationships between rectangular and polar coordinates are \( x = r\cos(\theta) \) and \( y = r\sin(\theta) \).
03
Substitute Rectangular to Polar
Substitute \( x = r\cos(\theta) \) and \( y = r\sin(\theta) \) into the equation \( y^2 = 4x \). This results in \( (r\sin(\theta))^2 = 4(r\cos(\theta)) \).
04
Simplify the Polar Equation
Expand and simplify: \( r^2\sin^2(\theta) = 4r\cos(\theta) \). To simplify, divide both sides by \( r \) (assuming \( r eq 0 \)) to get \( r\sin^2(\theta) = 4\cos(\theta) \). This is the polar form of the equation.
05
Analyze and Sketch the Graph
The polar equation \( r\sin^2(\theta) = 4\cos(\theta) \) describes a conic section. Since it originates from \( y^2 = 4x \), it remains a parabola but expressed in terms of polar coordinates. The sketch will be identical to the parabola \( y^2 = 4x \) opening in the positive direction along a radial line.
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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 on a plane using two numbers: the x-coordinate and the y-coordinate. These numbers tell how far along the axis a point is from the origin, which is the center point (0,0) on the Cartesian plane. This system is also known as Cartesian coordinates.
In rectangular coordinates:
In rectangular coordinates:
- The x-coordinate shows how far left or right a point is from the x-axis.
- The y-coordinate shows how far up or down a point is from the y-axis.
Parabola
A parabola is a specific type of curve on a graph, shaped like an arch. It can open up, down, left, or right depending on how its equation is structured. In our exercise, the equation given is \( y^2 = 4x \), which represents a parabola.
Key characteristics of a parabola:
Key characteristics of a parabola:
- It has a single peak or vertex, which in the equation \( y^2 = 4x \) is at the origin (0,0).
- It is symmetric, meaning one side is a mirror of the other.
- This particular parabola opens to the right, shown by the equation having \( x \) alone on one side.
Conic Sections
Conic sections are shapes created as a plane intersects a cone. These sections include circles, ellipses, parabolas, and hyperbolas. Each conic section has specific equations and forms based on this intersection.
What makes parabolas a conic section:
What makes parabolas a conic section:
- A parabola occurs when a plane is parallel to the slant of the cone.
- These can be expressed in standard form, such as \( y^2 = 4x \) for a parabola, showing their unique structure.
- They are important in fields like physics, engineering, and astronomy.