Calculating Area of Polar Curve: Help Needed!

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SUMMARY

The discussion centers on calculating the area of the polar curve defined by the equation r² = 9cos(5θ). The user initially selected the interval from 0 to π/2 but received an incorrect area result of 18/5, while the textbook states the correct area is 18. It was clarified that the chosen interval does not encompass the entire curve, as the cosine function must be positive to yield valid points on the curve. Key points include the need to visualize the curve and understand the behavior of cos(5θ) within the specified interval.

PREREQUISITES
  • Understanding of polar coordinates and polar curves
  • Knowledge of trigonometric functions, specifically cosine
  • Familiarity with integration techniques for area calculation
  • Ability to sketch polar curves to visualize their behavior
NEXT STEPS
  • Study the method for calculating areas of polar curves using integration
  • Learn about the properties of the cosine function and its periodicity
  • Explore the concept of symmetry in polar graphs to determine appropriate intervals
  • Practice sketching polar curves for various equations to improve visualization skills
USEFUL FOR

Students preparing for calculus exams, educators teaching polar coordinates, and anyone interested in mastering the area calculations of polar curves.

schaefer
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I've got a test tomorrow and I can't figure this one out:

r[tex]^{2}[/tex] = 9cos(5[tex]\vartheta[/tex])

I picked the inteval from 0 to [tex]\pi[/tex]/2 and I keep getting 18/5 but the back of the book says the answer is 18. I think something is wrong with my interval. Help Please!
 
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when the angle changed from 0 to pi/2 ,you DON'T get the whole curve!
Try drawing out the curve.Note, cos(5*angle) must be > 0 to give a real point on the curve.

when angle=0, r=3
when angle=18 degree, r=0hope this is helpful
 

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