/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 11 Sketch the curves over the inter... [FREE SOLUTION] | 91Ó°ÊÓ

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Sketch the curves over the interval \([0,2 \pi]\) unless otherwise stated. $$ r=\frac{1}{2}+\cos \theta $$

Short Answer

Expert verified
Sketch the limaçon with a dimple using key points and observing symmetry over \([0, 2\pi]\).

Step by step solution

01

Understanding Polar Equation

The given equation is in the polar form: \( r = \frac{1}{2} + \cos \theta \). This represents a polar curve where \( r \) varies with \( \theta \). Our task is to sketch this curve over the interval \( [0, 2\pi] \).
02

Identify Type of Curve

The equation \( r = 1 + a\cos\theta \) (where \( a > -1 \)) represents a limaçon with an inner loop. Here, \( a = \frac{1}{2} \). Since \( -1 < \frac{1}{2} < 1 \), this suggests a limaçon with a dimple, rather than a loop.
03

Range of \( r \)

Evaluate the maximum and minimum values of \( r \). When \( \cos \theta = 1 \), \( r = \frac{1}{2} + 1 = \frac{3}{2} \). When \( \cos \theta = -1 \), \( r = \frac{1}{2} - 1 = -\frac{1}{2} \). Hence, the range for \( r \) is from \(-\frac{1}{2}\) to \(\frac{3}{2}\).
04

Calculate Key Points

Find \( r \) at key angles: - For \( \theta = 0 \): \( r = \frac{1}{2} + 1 = \frac{3}{2} \)- For \( \theta = \frac{\pi}{2} \): \( r = \frac{1}{2} + 0 = \frac{1}{2} \)- For \( \theta = \pi \): \( r = \frac{1}{2} - 1 = -\frac{1}{2} \)- For \( \theta = \frac{3\pi}{2} \): \( r = \frac{1}{2} + 0 = \frac{1}{2} \)These points will help in sketching the curve.
05

Plot the Curve

Start from \( \theta = 0 \) where \( r = \frac{3}{2} \) and proceed to \( 2\pi \). Plot points gradually, noting how \( r \) changes with \( \theta \). The curve will have a dimple due to the negative \( r \) value at \( \theta = \pi \). Connect all the points to form the complete limaçon.

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Key Concepts

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

³¢¾±³¾²¹Ã§´Ç²Ô
A ³¢¾±³¾²¹Ã§´Ç²Ô is a type of polar curve that can look like a heart or a distorted circle. It all depends on the values in its equation. In our given equation, \( r = \frac{1}{2} + \cos \theta \), we see that this is a specific kind of ³¢¾±³¾²¹Ã§´Ç²Ô.

The general form of a ³¢¾±³¾²¹Ã§´Ç²Ô equation is \( r = a + b\cos\theta \) or \( r = a + b\sin\theta \). Here, \( a \) and \( b \) determine the shape. For our case, since \( a = 1/2 \) and \( b = 1 \), it suggests a ³¢¾±³¾²¹Ã§´Ç²Ô with a dimple.

Here are the varieties of ³¢¾±³¾²¹Ã§´Ç²Ôs based on the values of \( a \) and \( b \):
  • If \( |b| < |a| \): The ³¢¾±³¾²¹Ã§´Ç²Ô has a dimple.
  • If \( |b| = |a| \): The ³¢¾±³¾²¹Ã§´Ç²Ô forms a cardioid shape.
  • If \( |b| > |a| \): There is an inner loop in the ³¢¾±³¾²¹Ã§´Ç²Ô.
In our curve, since \( |b| = 1\) is larger than \( |a| = 1/2 \), but less than 1, we confirm it as a ³¢¾±³¾²¹Ã§´Ç²Ô with a dimple. This means it will look like a distorted circle with a little dip on one side.
Graphing Polar Curves
Graphing polar curves like the ³¢¾±³¾²¹Ã§´Ç²Ô can be an exciting journey. Instead of the regular x and y coordinates, plotting polar curves involves navigating through angles and radii.

Let's break down how to graph our curve, \( r = \frac{1}{2} + \cos \theta \):
  • **Determine Key Points**: Analyze the equation at various angles. Important angles to check are \( \theta = 0, \frac{\pi}{2}, \pi, \frac{3\pi}{2} \). These will guide the overall shape.
  • **Convert to Cartesian Coordinates**: Sometimes, plotting is easier in the Cartesian system. Use the formulas:
    \( x = r\cos\theta \)
    \( y = r\sin\theta \)
    This can help verify the polar plot in familiar coordinate system.
  • **Connect Points Smoothly**: Once points are marked, connect them smoothly as the curve naturally flows. The ³¢¾±³¾²¹Ã§´Ç²Ô’s dimple should be evident at \( \pi \) or 180 degrees.
As you sketch, you'll see how the curve swells out and dips in, characteristic of ³¢¾±³¾²¹Ã§´Ç²Ôs. Just like connecting dots, but with flair!
Range of Polar Functions
Understanding the range of polar functions is like seeing the reach of the curve as it spins around the origin. It tells us how far or how close the curve gets to the origin at any given angle, \( \theta \).

For our curve, \( r = \frac{1}{2} + \cos \theta \), let's determine the range of \( r \):
  • **Check Extremes**: The value of \( \cos \theta \) oscillates between \(-1\) and \(1\). Thus, \( r \) reaches its maximum when \( \cos \theta = 1 \) and its minimum when \( \cos \theta = -1 \). Thus, \( r \) ranges from \(-\frac{1}{2}\) to \(\frac{3}{2}\).
  • **How \( r \) Behaves**: Positive \( r \) values show the curve extending outward. Negative values mean the curve doubles back through the origin, making that dimple shape.
This range is crucial because it impacts what we see when sketching our polar curve. The ³¢¾±³¾²¹Ã§´Ç²Ô shows how polar functions can twist and fold in ways that linear graphs can't. Which makes them intriguing to explore.

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