1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Indefinite Integral

  1. Dec 6, 2009 #1
    1. The problem statement, all variables and given/known data

    [tex] \int{ x^3 \sqrt{(36-x^2)}dx} [/tex]

    2. Relevant equations

    3. The attempt at a solution

    I tried using trig substitution but got [tex] 7776\int{cos^3(\theta)-cos^5(\theta)d\theta} [/tex] which seems completely wrong


    [tex] \int{ (6cos(\theta))^36sin(\theta)6sin(\theta)d\theta [/tex]
  2. jcsd
  3. Dec 6, 2009 #2


    User Avatar
    Science Advisor

    You have an odd number of "x"s outside the square root so try this: Write the integral as [itex]\int x^2\sqrt{36- x^2}(x dx)[/itex] and let u= 36- x2. Then du= 2x dx so x dx= (1/2)du and [itex]x^2= 36- u[/itex].
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook