How to Graph Advanced Polar Equations with Symmetry (Precalculus - Trigonometry 42)

Professor-Leonard

How to Graph Advanced Polar Equations with Symmetry (Precalculus - Trigonometry 42) by Professor-Leonard

This video tutorial on precalculus and trigonometry teaches viewers to graph advanced polar equations with symmetry. The presenter explains how to check for different types of symmetry in polar equations and how to use this symmetry to simplify the process of plotting points. They provide several examples of using symmetry to graph polar equations and emphasize the importance of understanding symmetry to easily plot complex polar curves. Additionally, the video discusses how certain equations may only exist in two quadrants due to values resulting in imaginary numbers when using sine.

00:00:00

In this section, the instructor discusses how to graph advanced polar equations with symmetry. He explains that some equations do not work well in rectangular coordinates and that it is easier to leave them in polar. The instructor then explains that in order to check for symmetry, one should plug in negative theta and see if it gives the same exact equation as before. If so, there is symmetry about the polar axis or the x-axis. If negative pi plus theta gives you the same values as before, then it is symmetric about pi over two. Lastly, if changing just the value of r and the sine of r gives you the same equation, then there is symmetry about the pole. The instructor then walks the viewer through an example of how to use these techniques to graph r equals 1 minus sine theta.

00:05:00

In this section, the speaker discusses how to identify if a polar equation is symmetric and where it has symmetry. They go over the properties of sine and cosine and use sum and difference formulas to determine symmetry about the polar or x-axis and the pi over 2 axis or the y-axis. They also explain how to confirm symmetry about the origin or the pole, and discuss the advantages of using symmetry to avoid plotting all the points of a polar equation. If symmetry does not exist, the only way to proceed is to plot points manually.

00:10:00

In this section, the video explains how to find polar coordinates for values from negative pi over 2 to pi over 2 and use them to plot polar graphs. Although there is no symmetry about the pole, there is symmetry about the y-axis or about the pi over two axis, which allows us to find all the necessary values by mirroring them. By plugging in common angles, such as negative pi over 2 and negative pi over 3, into the polar equation, the distance from the pole can be determined. These values are then plotted on the graph to create the polar curve. Although we are plugging in values from negative pi over 2 to pi over 2, we don't have symmetry across the polar axis as sine is not symmetric about that axis.

00:15:00

In this section, the speaker discusses graphing advanced polar equations with symmetry. They begin by showing an example of the equation r=1-sin(theta), and explain the process of using symmetry to avoid having to plug in all values around the unit circle. They then demonstrate how to graph the equation r=1+2cos(theta), by checking for symmetry and using a sum or difference formula to simplify the equation. The speaker emphasizes the importance of identifying symmetry in polar equations to make graphing easier, and suggests using known values on a unit circle to simplify the calculations.

00:20:00

In this section, the presenter explains how to determine symmetry when graphing advanced polar equations. The presenter demonstrates how to simplify an equation and determine whether it is symmetric about the pole, polar axis, or line. After simplifying, the presenter shows how to plug in values from 0 to pi to determine where to plot points to obtain the graph. Points along the unit circle can also be included to obtain the best picture possible.

00:25:00

In this section, we learn how to graph advanced polar equations with symmetry using examples. The first example involves plugging in angles to find the corresponding coordinates along a ray, while the second example involves using symmetry to simplify the equation and find interesting properties. By understanding the symmetry of polar equations, we can easily graph complex and interesting shapes.

00:30:00

In this section of the video, the presenter explains the concept of symmetry in polar equations and shows how to graph advanced polar equations with the help of symmetry. They demonstrate how to identify whether a polar equation has symmetry and how to use symmetry to plot points on a unit circle. The presenter also explains how to use symmetry to graph symmetrical shapes such as roses.

00:35:00

In this section, the speaker explains how to graph advanced polar equations with symmetry in precalculus trigonometry. He emphasizes the importance of checking symmetry before plugging in values to limit the number of points you have to plot, and then using symmetry to mirror the graph. The last example he presents is symmetric about the pole, and he suggests checking two consecutive quadrants to plot the graph using polar coordinates.

00:40:00

In this section, the instructor explains how to find r in polar equations and how to use symmetry about the pole. When taking a square root to find r, it's necessary to consider both positive and negative values, leading to symmetry. For example, at pi over six in a given equation, you can add or subtract the square root of 2.8, which is around plus or minus 1.9 when calculated. Symmetry about the pole is achieved by plotting these values in both the positive and negative directions. Using this same method, the instructor shows the symmetry around the pole in equations evaluated at pi over four and pi over three. Additionally, when the equation evaluates to negative values, the resulting negative square root then becomes imaginary.

00:45:00

In this section, the speaker explains that some polar graphs may only exist in two quadrants due to the fact that certain values of sine will result in imaginary numbers. Therefore, the graph will not make sense when plotted on the polar coordinate system. The speaker also mentions the importance of understanding symmetry when graphing polar equations, as it can limit the amount of points that need to be plugged in and makes graphing certain equations much easier. Finally, the speaker introduces the concept of a Lemniscate, a type of graph that can only exist in two quadrants due to its symmetry.

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