Hey, everyone. In this problem, we're asked to graph the equation r 2 = 25 ∙ cos 2 · θ . Now here, this is the equation for a lemniscate because I have this r 2 , which I know is only something that happens when dealing with equations of lemniscates. Now, lemniscates are arguably our easiest shape that we know how to graph, so let's dive right in here. Now looking at our first step, we want to plot our first petal here, which is going to be located at 25 for our r value, and then we need to determine what θ is based on the trigonometric function that we're dealing with. Now, remember that in our equation, this value at the beginning is actually a squared. So, we need to make sure that we take the square root of that to get a. Now the square root of 25 is equal to 5, so this gives me my value of a that I will be plotting for that first petal. Now, we need to determine what θ is. Here, I have 25 times the cosine of 2θ. So, I'm dealing with a positive r2 and a cosine, which tells me that θ will be located at 0. So, I can plot my very first petal at 5, which will end up being right here on my polar axis. Now, all that's left to do is reflect this petal over the pole. So, doing that here, reflecting this over to the other side, landing me right here. I have my second petal, and I can move on to my final step and just connect these with a smooth and continuous curve. Now we know that the general shape of our lemniscate is a sort of infinity symbol or a propeller or whatever you want to think of this as, but remember that we're always going to go to that hole in there with these sorts of petals or propellers or whatever you want to call these. Now, we've graphed this lemniscate at r 2 = 25 ∙ cos 2 · θ . Let me know if you have any questions.
Table of contents
- 0. Fundamental Concepts of Algebra3h 29m
- 1. Equations and Inequalities3h 27m
- 2. Graphs1h 43m
- 3. Functions & Graphs2h 17m
- 4. Polynomial Functions1h 54m
- 5. Rational Functions1h 23m
- 6. Exponential and Logarithmic Functions2h 28m
- 7. Measuring Angles39m
- 8. Trigonometric Functions on Right Triangles2h 5m
- 9. Unit Circle1h 19m
- 10. Graphing Trigonometric Functions1h 19m
- 11. Inverse Trigonometric Functions and Basic Trig Equations1h 41m
- 12. Trigonometric Identities 2h 34m
- 13. Non-Right Triangles1h 38m
- 14. Vectors2h 25m
- 15. Polar Equations2h 5m
- 16. Parametric Equations1h 6m
- 17. Graphing Complex Numbers1h 7m
- 18. Systems of Equations and Matrices1h 6m
- 19. Conic Sections2h 36m
- 20. Sequences, Series & Induction1h 15m
- 21. Combinatorics and Probability1h 45m
- 22. Limits & Continuity1h 49m
- 23. Intro to Derivatives & Area Under the Curve2h 9m
15. Polar Equations
Graphing Other Common Polar Equations
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