# 2 | FRQ (Calculator Active) | Practice Sessions | AP Calculus BC

TLDRIn this AP review session, Tony Record and Bryan Passwater delve into polar equations, focusing on finding the area of a polar curve, determining the point where the curve is furthest from the origin, calculating the average distance from the curve to the y-axis, and integrating velocity to find the total distance traveled by a particle along the curve. They emphasize the importance of accuracy, using the correct units, and understanding the context of the problem to answer AP exam questions effectively.

###### Takeaways

- ๐ The session focuses on reviewing polar equations and their applications in the context of the AP exam.
- ๐ The first problem involves finding the area of a region bounded by a polar curve and the y-axis, which requires using a calculator and understanding the polar area formula.
- ๐ To find the area, one must determine the correct lower and upper limits of integration, which are the starting and ending points of the region.
- ๐ The lower limit is found by setting the polar equation to zero at the origin, resulting in 0.6417 (denoted as K).
- ๐ The upper limit is determined by the graph and is identified as pi/2.
- ๐งฎ The area calculation yields a result of 0.235, emphasizing the importance of accuracy to three decimal places as required by the AP exam.
- ๐ข Part B of the problem asks for the value of theta when the graph is furthest from the origin, which is an absolute extrema problem.
- ๐ To solve for the absolute extrema, one must consider critical values and endpoints, and then evaluate the original function at these points to find the maximum distance.
- ๐ The average distance from the graph of r(theta) to the y-axis over the interval 0 to pi is found by considering the absolute value of r(theta) and using the average value formula.
- ๐ Part D introduces a new function and a time component, describing a particle moving along the polar curve with velocity v(t) = r(t), and asks for the integral of the absolute value of v(t) from 0 to 6 seconds.
- ๐ The integral of the absolute value of velocity represents the total distance traveled by the particle, and the answer must be interpreted with context, units, and the time interval.

###### Q & A

### What is the main topic of the video?

-The main topic of the video is the review of polar equations and their applications in solving problems related to area, distance, and motion in the context of the AP Calculus exam.

### What is the polar curve equation discussed in the video?

-The polar curve equation discussed is r(theta) = sqrt(theta) - cos(theta), where r represents the radial distance and theta is the angle in polar coordinates.

### How is the area of region r found in the video?

-The area of region r is found using the formula for polar area, which is one-half times the integral from alpha to beta of the polar expression squared. The lower limit is the origin (0), and the upper limit is found by setting the polar equation to zero using a calculator, which is approximately 0.6417 (denoted as K). The integral is then calculated to find the area.

### What is the significance of the 0.6417 value found in the video?

-The value of 0.6417 (denoted as K) is the lower limit of integration for finding the area of region r. It is the value of theta at which the polar equation equals zero, representing the starting point of the region in question.

### How is the upper limit of theta determined in the problem?

-The upper limit of theta is determined by using intuition and the graph provided in the problem. It is found to be pi/2, which is the point at which the curve reaches its highest point in the first quadrant before the interval from 0 to 2 pi.

### What does part B of the problem ask for?

-Part B of the problem asks for the value of theta between 0 and 2 pi when the graph of r(theta) is furthest from the origin, and to justify the answer.

### How is the absolute maximum distance from the origin found in the video?

-The absolute maximum distance from the origin is found by identifying critical values of the function where the derivative equals zero or is undefined, and then evaluating the original function at these critical values and the endpoints of the interval. The largest value among these, considering the absolute value, gives the furthest point from the origin.

### What is the integral of the absolute value of v(t) interpreted as in the context of the problem?

-The integral of the absolute value of v(t) is interpreted as the total distance traveled by the particle, with the units being in feet since the velocity is given in feet per second.

### What is the significance of the average distance from the graph of r(theta) to the y-axis?

-The average distance from the graph of r(theta) to the y-axis represents the mean value of the distance the curve is from the y-axis over the interval from 0 to pi. This is found by integrating the absolute value of r(theta) times the cosine of theta over the interval and dividing by the length of the interval.

### How does the video emphasize the importance of accuracy in the AP exam?

-The video emphasizes the importance of accuracy by reminding students that answers must be accurate to at least three decimal places in the free response portion of the AP exam. It highlights the loss of potential points due to rounding errors and encourages careful checking of calculator entries.

### What is the main takeaway from the video regarding the use of technology in solving polar equations?

-The main takeaway is that while technology, such as graphing calculators, is useful for finding critical values and integrating functions, students should be familiar with how to use these tools effectively and should always verify their results to ensure accuracy.

###### Outlines

##### ๐ Introduction to Polar Equations and Area Calculation

The video begins with Tony Record and Bryan Passwater introducing the second session of the AP review, focusing on polar equations. They discuss a specific problem involving a polar curve r(theta) = sqrt(theta) - cos(theta) and its shaded region in the first quadrant. The main task is to find the area of this region, which requires using a calculator and understanding the boundaries of the integral. The lower limit is found to be 0.6417 (denoted as K) and the upper limit is pi/2. The process emphasizes the importance of accurate calculations and adhering to the AP exam's requirement of three decimal places in the free response section.

##### ๐ Finding the Maximum Distance from the Origin in Polar Coordinates

In this section, the focus shifts to finding the value of theta when the graph of r(theta) is furthest from the origin, which is an absolute maximum distance problem. The method involves identifying critical values where the derivative of r(theta) is zero or undefined. The derivative r'(theta) is calculated, and two critical values, labeled A and B, are found. To determine the absolute extremum, the original function r(theta) is evaluated at the endpoints and critical values. The largest value obtained, 2.811, indicates the furthest distance from the origin, considering the absolute value of r(theta) represents the distance from the y-axis.

##### ๐ Calculating the Average Distance from the y-Axis Using Polar Equations

The third part of the video discusses calculating the average distance from the graph of r(theta) to the y-axis over the interval from 0 to pi. The distance is represented by the absolute value of r(theta)cos(theta), which simplifies to r(theta) since cos(theta) is non-negative in the first quadrant. The average distance is then found using the integral formula, which yields a result of 0.891. This value represents the average distance from the y-axis over the specified interval.

##### ๐ Particle Motion on a Polar Curve and Calculating Total Distance Traveled

The final section introduces a new concept where a particle moves along the polar curve r(t) = sqrt(t) - cos(t), with the velocity given by r(t). The task is to find the integral of the absolute value of the velocity function from 0 to 6 seconds. This integral represents the total distance traveled by the particle. The calculation is performed using a calculator, resulting in a value of 10.589 feet. The interpretation of this value is emphasized, noting that it is the total distance traveled by the particle over the 6-second interval, with the correct units and context provided.

###### Mindmap

###### Keywords

##### ๐กPolar Equations

##### ๐กFree Response

##### ๐กArea Calculation

##### ๐กCalculator

##### ๐กAbsolute Extrema

##### ๐กCritical Values

##### ๐กAverage Distance

##### ๐กIntegration

##### ๐กPolar Coordinates

##### ๐กAccuracy

###### Highlights

The session focuses on solving intricate polar equation problems, specifically related to finding the area of a shaded region in polar coordinates.

The problem involves a polar curve r(theta) = sqrt(theta) - cos(theta) and finding the area of the region bounded by this curve and the y-axis in the first quadrant.

The solution requires the use of a calculator, emphasizing the importance of accuracy to at least three decimal places for the AP exam.

The method for finding the area involves using the polar area formula, which is 1/2 times the integral from alpha to beta of the squared polar expression.

Identifying the boundaries for integration is crucial, with the lower limit starting at the origin and the upper limit found using calculator technology to be pi/2.

The process of finding the area is detailed, including the use of technology for finding critical values and ensuring careful input of values into the calculator.

Part B of the problem involves finding the value of theta when the graph of r(theta) is furthest from the origin and justifying the answer.

The solution to part B involves understanding absolute extrema and differentiating the polar function to find critical values where the derivative equals zero.

The concept of absolute maximum distance from the origin is discussed, and it is related to the idea of r(theta), which gives the sine distance from the origin.

Part C focuses on finding the average distance from the graph of r(theta) to the y-axis over the interval 0 to pi.

The average distance is calculated by considering the positive distance from the y-axis, represented by r(theta)cos(theta) and using the absolute value.

The average value formula is used to find the average distance, with the integral calculated from 0 to pi, resulting in an answer of 0.891.

Part D introduces a new function and the concept of a particle moving along the polar curve, with the velocity given as r(t).

The integral of the absolute value of the velocity function v(t) is calculated from 0 to 6 seconds, resulting in a total distance traveled of approximately 10.589 feet.

The session emphasizes the importance of showing work and providing justification for answers, especially in the context of the AP exam.

The video provides tips on using calculator technology effectively for solving polar equation problems and finding critical values.

The session concludes with a reminder to check out previous review videos for more in-depth understanding of polar area type free response questions.

###### Transcripts

## Browse More Related Video

2022 Live Review 6 | AP Calculus BC | Working with Parametric Equations and Vectors

Polar, Parametric, Vector Multiple Choice Practice for Calc BC (Part 4)

Polar, Parametric, Vector Multiple Choice Practice for Calc BC (Part 1)

2021 Live Review 2 | AP Calculus BC | Preparing for Polar Equations Questions

1 | MCQ | Practice Sessions | AP Calculus BC

AP Calculus BC Lesson 9.8

5.0 / 5 (0 votes)

Thanks for rating: