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

Homework Help: I dont understand how antiderviative of 2 sin (2x) could be -cos(2x)

  1. Nov 23, 2004 #1
    i dont understand how the antiderviative of 2 sin (2x) could be -cos(2x), what happens to the 2?

    also how can the antiderivative of 5e^(5t) be e^(5t)?
  2. jcsd
  3. Nov 23, 2004 #2


    User Avatar

    Well, what do you get when you take the derivative of -cos2x? You apply the chain rule or whatever rule it is and come up with 2sin2x. Just like the 2 "appears" when taking the derivative, it also "disappears" when you take the antiderivative.

    As for the second one, Dx (e^x) = e^x, that's why the second one is true.

    If in doubt concerning an antiderivative, just check by taking the derivative of the answer you found.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook