Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Area of polar curve

  1. Oct 1, 2007 #1
    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!
  2. jcsd
  3. Oct 1, 2007 #2
    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=0

    hope this is helpful
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook